UE 4.8 P4 Hangs on project save


I found some interesting bug - when I trying to save project in UE 4.8 P4 with running project - UE hangs.
How to reproduce:

  1. Open project in UE 4.8 P4

  2. Change something on scene

  3. Run game - Alt+P

  4. Press Save button in UE Editor

  5. You will see something like


  1. Press OK button

Now two ways:

First way:

  1. UE will hangs and will crash

Second way:

  1. You will message error log

  2. Close message log

  3. Press Stop button in Editor

  4. UE will eats a lot of RAM, will hung


  1. You will get error:



Unknown exception - code 00000001 (first/second chance not available)

"Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.8\Engine\Source\Developer\MessageLog\Private\Model\MessageLogListingModel.cpp] [Line: 70]
Critical E

UE4Editor_Core!FOutputDeviceWindowsError::Serialize() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95]
UE4Editor_Core!FOutputDevice::Logf__VA() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:144]
UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:360]
UE4Editor_Core!FMsg::Logf__VA() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:528]
UE4Editor_MessageLog!FMessageLogListingModel::AddMessageInternal() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\messagelog\private\model\messageloglistingmodel.cpp:70]
UE4Editor_MessageLog!FMessageLogListingModel::AddMessages() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\developer\messagelog\private\model\messageloglistingmodel.cpp:89]
UE4Editor_Core!FMessageLog::Flush() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\logging\messagelog.cpp:188]
UE4Editor_Core!FMessageLog::~FMessageLog() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\logging\messagelog.cpp:91]
UE4Editor_UnrealEd!UEditorEngine::EndPlayMap() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:267]
UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\editorengine.cpp:1571]
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\unrealedengine.cpp:366]
UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launchengineloop.cpp:2355]
UE4Editor!GuardedMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:200]

Hello, .

No, it’s project with existing content…

Here is archive with whole Logs folder:
link text

Errors like this occurs very often for me…

I have about 5 restarts with losing of changes in my “game”.


Does this occur in a blank project with no additional content or is this specific to your project? Additionally, can you post your crash logs, they can be found at \Unreal Projects\PROJECTNAME\saved\logs.


I’m not sure, but…

Last exception occurred after editing of Lights (How to rebuild lights programmatically? - Rendering - Epic Developer Community Forums)

Another exceptions occurred after editing of the Level Blueprint and Static Mesh Blueprint’s Construction Script…

I find it difficult to answer more precisely.

I did not pay attention to the causes of crashes.

Here is crash logs from another project with same symptoms

link text

Here is dxdiag link text

First logs (235.7 kB) from project, which created in UE 4.8 P4.

Second logs (698.3 kB) created in 4.7.6 and opened in 4.8 P4.

What were the most recent changes you made to the project before this started occurring?

Can you post your dxdiag here? Additionally how large are the projects you are working with? Were they created in 4.8 or did you update them from another engine version?

What type of graphics card are you currently using? The dxdiag says it is an integrated intel HD but gives no specific model.

NVIDIA GeForce GT740M.
Driver’s version at that point - v. 350
Now I’ve installed v 353.06

Still able to reproduce. I made video, how to hang UEwww…com/watch?v=jHUQgDp32IA&feature=youtu.be

link text

Can you send me a copy of your project? I’d be happy to take a look and see what may be occurring.



I was able to reproduce this and have entered a bug report, UE-16695 to be assessed by the development staff. The functionality you have in your level blueprint is the source of the crash. If you move it to a character blueprint, the project will save without hanging or crashing.


Thank you for advice!