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[LINUX UE4Editor] Signal 11 CRASH + RFE / Workaround?

Hi, im new to UE4, and have enjoyed going through a few learning paths and projects I just downloaded the latest repo (4.26.1) off of github and was quite happy to with the ease of the build process on fedora 33 tbh. The the Quixel Bridge AppImage just blew my mind.

Unfortunately, I have been hitting consistently repeatable crashes in what could be the worst possible spot.
Essentially, every time I attempt to Drag and Drop from the Content Browser or Place Actors Tab into the Viewport I get a segfault. It doesn’t matter if its an existing project or a blank project and dragging any item from the Place Actors Tab will do it. I’ve searched the forums a decent amount and haven’t found anything related to this.

In searching the docs, I was able to find a workaround for the Content Browser for now, where instead of dragging and dropping I can select what I want in the Content Browser, then RMB in the viewport to get a context menu where I can get an asset and a couple of light types into the level without D&D. However I cant find any similar workaround for the Place Actors pane. D&D seems to work fine between the context browser and other editors (ie Textures and Materials), however it also crashes when I try and place from the Class Viewer. It would be great if you could use a modifier key (like Houdini for example) to Ctrl+Click a selection from these locations into the level at the origin. I find it hard to believe there is no other way to do this other than drag and drop. Am I missing something?

I’m not sure if there is a chance I may have missed installing some libraries on my workstation. I have been relying on NVIDIA drivers for vulkan GPU support on my RTX 2060 Super, which all works great with a DCC like Houdini for instance. At any rate, I have mashed the send crash report button a bunch of times, but thought I’d post some of the crash logs here In case someone can offer some advice. I have also tried -opengl4 and -vulkanvalidation=5 based on forum suggestions, but neither make any difference.

I can try to crack this open in Kdevelop or QtCreator, but don’t really have an idea where to start looking or what to consider atm.
Null pointer/memory clobbered/sql db handle/driver/lib issue/RHI?
Any advice would be appreciated, thanks.

The crash window / Diagnostics.txt reports:



Assertion failed: !GIsRHIInitialized || !GRHISupportsRHIThread [File:Runtime/RHI/Public/RHIStaticStates.h] [Line: 98]

libUE4Editor-Core.so!FGenericPlatformMisc::RaiseException(unsigned int) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/GenericPlatform/GenericPlatformMisc.cpp:472]
libUE4Editor-Core.so!FOutputDevice::LogfImpl(char16_t const*, ...) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/OutputDevice.cpp:61]
libUE4Editor-Core.so!AssertFailedImplV(char const*, char const*, int, char16_t const*, __va_list_tag*) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:104]
libUE4Editor-Core.so!FDebug::CheckVerifyFailedImpl(char const*, char const*, int, char16_t const*, ...) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:458]
libUE4Editor-ChaosNiagara.so!TStaticStateRHI<TStaticSamplerState<(ESamplerFilter)1, (ESamplerAddressMode)1, (ESamplerAddressMode)1, (ESamplerAddressMode)1, 0, 1, 0u, (ESamplerCompareFunction)0>, TRefCountPtr<FRHISamplerState>, FRHISamplerState*>::FStaticStateResource::~FStaticStateResource() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/RHI/Public/RHIStaticStates.h:98]
libc.so.6!UnknownFunction(0x40236)
libc.so.6!exit(+0x1f)
libX11.so.6!_XDefaultError(+0x3a)
libX11.so.6!_XError(+0xfa)
libX11.so.6!UnknownFunction(0x4c226)
libX11.so.6!_XReply(+0x422)
libX11.so.6!XTranslateCoordinates(+0x8a)
libUE4Editor-ApplicationCore.so!X11_SetWindowPosition [/SDL-gui-backend/src/video/x11/SDL_x11window.c:876]
libUE4Editor-ApplicationCore.so!SDL_SetWindowPosition_REAL [/SDL-gui-backend/src/video/SDL_video.c:1962]
libUE4Editor-SlateCore.so!FDragDropOperation::OnDragged(FDragDropEvent const&) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/SlateCore/Private/Input/DragAndDrop.cpp:45]
libUE4Editor-Slate.so!FSlateUser::NotifyPointerMoveComplete(FPointerEvent const&, FWidgetPath const&) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateUser.cpp:974]
libUE4Editor-Slate.so!FSlateApplication::RoutePointerMoveEvent(FWidgetPath const&, FPointerEvent const&, bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication.cpp:5200]
libUE4Editor-Slate.so!FSlateApplication::ProcessMouseMoveEvent(FPointerEvent const&, bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication.cpp:5594]
libUE4Editor-Slate.so!FSlateApplication::OnMouseMove() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication.cpp:5518]
libUE4Editor-ApplicationCore.so!FLinuxApplication::ProcessDeferredMessage(SDL_Event) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/ApplicationCore/Private/Linux/LinuxApplication.cpp:336]
libUE4Editor-ApplicationCore.so!FLinuxPlatformApplicationMisc::PumpMessages(bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/ApplicationCore/Private/Linux/LinuxPlatformApplicationMisc.cpp:428]
UE4Editor!FEngineLoop::Tick() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Launch/Private/LaunchEngineLoop.cpp:4748]
UE4Editor!GuardedMain(char16_t const*) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Launch/Private/Launch.cpp:171]
libUE4Editor-UnixCommonStartup.so!CommonUnixMain(int, char**, int (*)(char16_t const*), void (*)()) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Unix/UnixCommonStartup/Private/UnixCommonStartup.cpp:264]
libc.so.6!__libc_start_main(+0xf1)
UE4Editor!_start()


The project.log reports:




[2021.02.13-11.34.20:089]  0]LogCollectionManager: Fixed up redirectors for 0 collections in 0.000002 seconds (updated 0 objects)
[2021.02.13-11.34.20:132]  0]LogContentStreaming: Texture pool size now 1000 MB
[2021.02.13-11.34.20:293]  0]LogRenderer: Reallocating scene render targets to support 1052x728 Format 10 NumSamples 1 (Frame:2).
[2021.02.13-11.34.20:385]  2]LogCore: Done sending crash report for ensure().
**[2021.02.13-11.37.14:801] 82]LogActorFactory: Actor Factory created Plane**
[2021.02.13-11.37.14:823] 82]LogOutputDevice: Warning:  

Script Stack (0 frames):

[2021.02.13-11.37.14:825] 82]LogCore: Error: appError called: Assertion failed: !GIsRHIInitialized || !GRHISupportsRHIThread [File:Runtime/RHI/Public/RHIStaticStates.h] [Line: 98]  


[2021.02.13-11.37.14:875] 82]LogCore: === Critical error: ===
**Unhandled Exception: SIGSEGV: invalid attempt to write memory at address 0x0000000000000003**

[2021.02.13-11.37.14:875] 82]LogCore: Assertion failed: !GIsRHIInitialized || !GRHISupportsRHIThread [File:Runtime/RHI/Public/RHIStaticStates.h] [Line: 98]  



0x00007efe339cc06e libUE4Editor-Core.so!FGenericPlatformMisc::RaiseException(unsigned int) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/GenericPlatform/GenericPlatformMisc.cpp:472]
0x00007efe33c1710b libUE4Editor-Core.so!FOutputDevice::LogfImpl(char16_t const*, ...) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/OutputDevice.cpp:61]
0x00007efe33b976b6 libUE4Editor-Core.so!AssertFailedImplV(char const*, char const*, int, char16_t const*, __va_list_tag*) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:104]
0x00007efe33b9754b libUE4Editor-Core.so!FDebug::CheckVerifyFailedImpl(char const*, char const*, int, char16_t const*, ...) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Core/Private/Misc/AssertionMacros.cpp:458]
0x00007efcb204df72 libUE4Editor-ChaosNiagara.so!TStaticStateRHI<TStaticSamplerState<(ESamplerFilter)1, (ESamplerAddressMode)1, (ESamplerAddressMode)1, (ESamplerAddressMode)1, 0, 1, 0u, (ESamplerCompareFunction)0>, TRefCountPtr<FRHISampl
erState>, FRHISamplerState*>::FStaticStateResource::~FStaticStateResource() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/RHI/Public/RHIStaticStates.h:98]
0x00007efe2ac9d237 libc.so.6!UnknownFunction(0x40236)
0x00007efe2ac9d3e0 libc.so.6!exit(+0x1f)
0x00007efd6d4a104b libX11.so.6!_XDefaultError(+0x3a)
0x00007efd6d4a114b libX11.so.6!_XError(+0xfa)
0x00007efd6d4a1227 libX11.so.6!UnknownFunction(0x4c226)
0x00007efd6d4a2d13 libX11.so.6!_XReply(+0x422)
0x00007efd6d4a2ebb libX11.so.6!XTranslateCoordinates(+0x8a)
0x00007efe2dfc46ea libUE4Editor-ApplicationCore.so!X11_SetWindowPosition [/SDL-gui-backend/src/video/x11/SDL_x11window.c:876]
0x00007efe2df49e82 libUE4Editor-ApplicationCore.so!SDL_SetWindowPosition_REAL [/SDL-gui-backend/src/video/SDL_video.c:1962]
0x00007efe2d4fd991 libUE4Editor-SlateCore.so!FDragDropOperation::OnDragged(FDragDropEvent const&) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/SlateCore/Private/Input/DragAndDrop.cpp:45]
0x00007efe2da1ff0e libUE4Editor-Slate.so!FSlateUser::NotifyPointerMoveComplete(FPointerEvent const&, FWidgetPath const&) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateUser.cpp:974]
0x00007efe2da1e006 libUE4Editor-Slate.so!FSlateApplication::RoutePointerMoveEvent(FWidgetPath const&, FPointerEvent const&, bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication
.cpp:5200]
0x00007efe2d9df83f libUE4Editor-Slate.so!FSlateApplication::ProcessMouseMoveEvent(FPointerEvent const&, bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication.cpp:5594]
0x00007efe2da238c1 libUE4Editor-Slate.so!FSlateApplication::OnMouseMove() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateApplication.cpp:5518]
0x00007efe2deb5728 libUE4Editor-ApplicationCore.so!FLinuxApplication::ProcessDeferredMessage(SDL_Event) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/ApplicationCore/Private/Linux/LinuxApplication.cpp:336]
0x00007efe2deb41e1 libUE4Editor-ApplicationCore.so!FLinuxPlatformApplicationMisc::PumpMessages(bool) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/ApplicationCore/Private/Linux/LinuxPlatformApplicationMisc.cpp:428]
0x0000000000266942 UE4Editor!FEngineLoop::Tick() [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Launch/Private/LaunchEngineLoop.cpp:4748]
0x0000000000276593 UE4Editor!GuardedMain(char16_t const*) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Launch/Private/Launch.cpp:171]
0x00007efe2ae37056 libUE4Editor-UnixCommonStartup.so!CommonUnixMain(int, char**, int (*)(char16_t const*), void (*)()) [/home/sdugaro/GIT/UnrealEngine/Engine/Source/Runtime/Unix/UnixCommonStartup/Private/UnixCommonStartup.cpp:264]
0x00007efe2ac851e2 libc.so.6!__libc_start_main(+0xf1)
0x000000000025f4c9 UE4Editor!_start()

[2021.02.13-11.37.14:883] 82]LogExit: Executing StaticShutdownAfterError
[2021.02.13-11.37.14:885] 82]LogAudioMixer: Display: Audio Buffer Underrun (starvation) detected.



The CrashContext.runtime-xml reports (in part)


      
<?xml version="1.0" encoding="UTF-8"?>
<FGenericCrashContext>
       <RuntimeProperties>
               <CrashVersion>3</CrashVersion>
               <ExecutionGuid>A9E641EAE99243958125DFEACCFE563B</ExecutionGuid>
               <CrashGUID>UE4CC-Linux-1A33CE066C5C4E15978B4F480B4AD639_0003</CrashGUID>
               <IsEnsure>false</IsEnsure>
               <IsAssert>true</IsAssert>
               <CrashType>Assert</CrashType>
               <ErrorMessage>Assertion failed: !GIsRHIInitialized || !GRHISupportsRHIThread [File:Runtime/RHI/Public/RHIStaticStates.h] [Line: 98]</ErrorMessage>
               <CrashReporterMessage />
               <ProcessId>125674</ProcessId>
               <SecondsSinceStart>446</SecondsSinceStart>
               <IsInternalBuild>false</IsInternalBuild>
               <IsPerforceBuild>false</IsPerforceBuild>
               <IsSourceDistribution>true</IsSourceDistribution>
               <GameName>UE4-MyProject3</GameName>
               <ExecutableName>UE4Editor</ExecutableName>
               <BuildConfiguration>Development</BuildConfiguration>
               <GameSessionID />
               <Symbols>**UE4*Release-4.26-CL-0-Linux-Development</Symbols>
               <PlatformName>Linux</PlatformName>
               <PlatformNameIni>Linux</PlatformNameIni>
               <EngineMode>Editor</EngineMode>
               <EngineModeEx>Dirty</EngineModeEx>
               <DeploymentName />
               <EngineVersion>4.26.1-0+++UE4+Release-4.26</EngineVersion>
               <CommandLine>"/home/sdugaro/Documents/Unreal Projects/MyProject3/MyProject3.uproject"</CommandLine>
               <LanguageLCID>0</LanguageLCID>
               <AppDefaultLocale>en_NZ</AppDefaultLocale>
               <BuildVersion>++UE4+Release-4.26-CL-0</BuildVersion>
               <IsUE4Release>false</IsUE4Release>
               <IsRequestingExit>false</IsRequestingExit>
               <UserName />
               <BaseDir>/home/sdugaro/GIT/UnrealEngine/Engine/Binaries/Linux/</BaseDir>
               <RootDir>/home/sdugaro/GIT/UnrealEngine/</RootDir>
               <MachineId>92B0701938A943D49EDD6D98C96FC7AD-000003E8</MachineId>
               <LoginId>92b0701938a943d49edd6d98c96fc7ad-000003e8</LoginId>
               <EpicAccountId />
               <SourceContext />
               <UserDescription />
               <UserActivityHint>Layout="LevelEditorViewport" Label="Viewport 1" Content=SViewpo</UserActivityHint>
               <CrashDumpMode>0</CrashDumpMode>
               <GameStateName />
               <Misc.NumberOfCores>8</Misc.NumberOfCores>
               <Misc.NumberOfCoresIncludingHyperthreads>8</Misc.NumberOfCoresIncludingHyperthreads>
               <Misc.Is64bitOperatingSystem>1</Misc.Is64bitOperatingSystem>
               <Misc.CPUVendor>GenuineIntel</Misc.CPUVendor>
               <Misc.CPUBrand>Intel(R) Xeon(R) CPU E5620 @ 2.40GHz</Misc.CPUBrand>
               <Misc.PrimaryGPUBrand>GenericGPUBrand</Misc.PrimaryGPUBrand>
               <Misc.OSVersionMajor>GenericOSVersionLabel</Misc.OSVersionMajor>
               <Misc.OSVersionMinor>GenericOSSubVersionLabel</Misc.OSVersionMinor>
               <MemoryStats.TotalPhysical>75877126144</MemoryStats.TotalPhysical>
               <MemoryStats.TotalVirtual>8589926400</MemoryStats.TotalVirtual>
               <MemoryStats.PageSize>4096</MemoryStats.PageSize>
               <MemoryStats.TotalPhysicalGB>71</MemoryStats.TotalPhysicalGB>
               <MemoryStats.AvailablePhysical>69568409600</MemoryStats.AvailablePhysical>
               <MemoryStats.AvailableVirtual>8589926400</MemoryStats.AvailableVirtual>
               <MemoryStats.UsedPhysical>1359073280</MemoryStats.UsedPhysical>
               <MemoryStats.PeakUsedPhysical>1377501184</MemoryStats.PeakUsedPhysical>
               <MemoryStats.UsedVirtual>7393419264</MemoryStats.UsedVirtual>
               <MemoryStats.PeakUsedVirtual>7423795200</MemoryStats.PeakUsedVirtual>
               <MemoryStats.bIsOOM>0</MemoryStats.bIsOOM>
               <MemoryStats.OOMAllocationSize>0</MemoryStats.OOMAllocationSize>
               <MemoryStats.OOMAllocationAlignment>0</MemoryStats.OOMAllocationAlignment>
               <NumMinidumpFramesToIgnore>0</NumMinidumpFramesToIgnore>
               <CallStack />
               <PCallStack>libUE4Editor-Core 0x00007efe33417000 + 5b506e libUE4Editor-Core 0x00007efe33417000 + 80010b libUE4Editor-Core 0x00007efe33417000 + 7806b6 libUE4Editor-Core 0x00007efe33417000 + 78054b libUE4Editor-ChaosNiagar
a 0x00007efcb1faf000 + 9ef72 libc.so 0x00007efe2ac5d000 + 40237 libc.so 0x00007efe2ac5d000 + 403e0 libX11.so 0x00007efd6d455000 + 4c04b libX11.so 0x00007efd6d455000 + 4c14b libX11.so 0x00007efd6d455000 + 4c227 libX11.so 0x00007efd6d4550
00 + 4dd13 libX11.so 0x00007efd6d455000 + 4debb libUE4Editor-ApplicationCore 0x00007efe2ddc6000 + 1fe6ea libUE4Editor-ApplicationCore 0x00007efe2ddc6000 + 183e82 libUE4Editor-SlateCore 0x00007efe2d28b000 + 272991 libUE4Editor-Slate 0x00
007efe2d7a0000 + 27ff0e libUE4Editor-Slate 0x00007efe2d7a0000 + 27e006 libUE4Editor-Slate 0x00007efe2d7a0000 + 23f83f libUE4Editor-Slate 0x00007efe2d7a0000 + 2838c1 libUE4Editor-ApplicationCore 0x00007efe2ddc6000 + ef728 libUE4Editor-Ap
plicationCore 0x00007efe2ddc6000 + ee1e1 UE4Editor 0x0000000000200000 + 66942 UE4Editor 0x0000000000200000 + 76593 libUE4Editor-UnixCommonStartup 0x00007efe2ae33000 + 4056 libc.so 0x00007efe2ac5d000 + 281e2 UE4Editor 0x0000000000200000
+ 5f4c9</PCallStack>
               <PCallStackHash>E1956B789D79C6670E6654807EA97EA3B79E673F</PCallStackHash>
               <TimeOfCrash>637488130352040000</TimeOfCrash>
               <bAllowToBeContacted>1</bAllowToBeContacted>
               <PlatformFullName>Linux [GenericOSVersionLabel GenericOSSubVersionLabel 64b]</PlatformFullName>
               <CrashReportClientVersion>1.0</CrashReportClientVersion>
       </RuntimeProperties>
       <PlatformProperties>
               <CrashSignal>11</CrashSignal>
               <CrashSignalName>Segmentation fault</CrashSignalName>
               <PlatformCallbackResult>0</PlatformCallbackResult>
       </PlatformProperties>
       <EngineData>
               <RHI.RHIName>Vulkan</RHI.RHIName>
               <RHI.AdapterName>GeForce RTX 2060 SUPER</RHI.AdapterName>
               <RHI.UserDriverVersion>460.39</RHI.UserDriverVersion>
               <RHI.FeatureLevel>SM5</RHI.FeatureLevel>
       </EngineData>
       <GameData />
       <EnabledPlugins>
               <Plugin>{ "Version": 1, "VersionName": "0.10", "FriendlyName": "Megascans" }</Plugin>
...
               <Plugin>{ "Version": 1, "VersionName": "1.0", "FriendlyName": "Online Subsystem GooglePlay" }</Plugin>
       </EnabledPlugins>
</FGenericCrashContext>





Nice to see there’s a Python API in 4.26!
This made me think it should be possible to create a Sky Light or Post Process Volume by script, as these are 2 Actors in the Place Actors list I cannot get into my scene without crashing the UE4Editor. While there are some thin docs on the python api, I cant seem to find any documentation on how one works with it. In my case, I just want to load an actor into my level/viewport, and was looking at the below method, however i’m not sure what arguments are expected or where I can find out more about them.


LogPython: help(unreal.load_object)
LogPython: Help on built-in function load_object in module _unreal_core:
load_object(...)
x.load_object(outer, name, type=Object, follow_redirectors=True) -> Object -- load an Unreal object with the given outer and name, optionally validating its type

ie. what is outer? a handle to the level in which to create the object? how does one get this?
I’m also assuming there is an underlying name for something like “Sky Light” or other labels in the place actors list. Is there a convention for this, or c++ names?

I’m going to poke around with cmd a bit, as there is likely more reference out there for that, and i’d expect one should be able to do this from there as well.

That was pretty easy. This python API is a bit foreign at first, but powerful.
This allows me to sidestep the D&D segfault and carry on with dialling the actor details as if it wasn’t an issue at all.
I dread to think what the time investment would have been like to try and sort this out in c++



# `][v][Python]
unreal.EditorLevelLibrary.spawn_actor_from_class(unreal.PostProcessVolume, unreal.Vector(0,0,0))
unreal.EditorLevelLibrary.spawn_actor_from_class(unreal.SkyLight, unreal.Vector(0,0,0))
unreal.EditorLevelLibrary.spawn_actor_from_class(unreal.CineCameraActor, unreal.Vector(0,0,0))


Heh, for reference, I just discovered another workaround that works great for me. RMB(Content Browser) > Blueprint Class [Actor]
This will bring up a component editor where the + Add Component] dropdown gives you access to all the /place actors\ options in the main window.
TBH, I think i prefer working this way, as opposed to dragging in toplevel actors, as it forces you to immediately group together all the primitive actors you want logically and up front. ie, a light rig, cinema camera setup with a backdrop (stage), your aggregate primitive subjects etc… kind of enforcing a logical world outline out of the gates, as opposed to dragging in actors, organising them in folders, grouping them, and ultimately Toolbar | Blueprint > Convert Selection to blueprint Class anyway.

Then this /place actors\ segfault can be avoided by selecting this new BP actor in the content browser and RMB(viewport) > to drop it in the scene.
Moreover, the individual components can be edited (affine repo) once in the viewport to further customise the instance, where any newly instantiated BP actors continue to come in with the defaults. Nicely analogous to HDAs for me. Houdini+Unreal+Python+Linux 4 Life!

If you are doing serious project then it would be better to use 4.25.4. This bug had been there from 4.24, but not in 4.25.4.
They have done a lot of change in this release cycle for linux and therefore 4.26.x has many new bugs in render core, SDL, and vulkan (too many). Basically on linux you should avoid using till its .3 release!

Thanks for the info. good to know. I can happily make due in the meantime as I would prefer to be on linux, and am still getting my bearings with UE4 anyway.
Ill just continue to submit bugs as I hit them, but other than some of this UI glitchiness, its been pretty solid.
In some ways, its kind of a good exercise to try and find workarounds.