UE5 Preview can't open any blueprints/maps

Development Programming & Scripting Blueprint
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1

Hi,

I have an issue with UE5 Preview (occurs in 1 & 2) which stops me running my project, even though it runs fine in 5.0EA and 4.27. It seems that any map or blueprint containing previously-made scripts will crash the editor. Simple data blueprints (like structures or enums, but not function libraries) will open normally though and I can create new objects and make scripts just fine. The crash only occurs when I try to edit something I previously made using another engine version.

Here’s the error I get:

Assertion failed: OutputPin->LinkedTo.Num() > 0 [File:D:\build++UE5\Sync\Engine\Source\Editor\KismetCompiler\Private\KismetCompiler.cpp] [Line: 301]

UnrealEditor_KismetCompiler
UnrealEditor_KismetCompiler
UnrealEditor_Kismet
UnrealEditor_Kismet
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
user32
user32
UnrealEditor_ApplicationCore
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

The log doesn’t show any errors, it crashes before reporting anything, however I do notice these errors when the project opens:

LogWindows: Failed to load ‘aqProf.dll’ (GetLastError=126)
LogWindows: File ‘aqProf.dll’ does not exist
LogProfilingDebugging: Loading WinPixEventRuntime.dll for PIX profiling (from …/…/…/Engine/Binaries/ThirdParty/Windows/WinPixEventRuntime/x64).
LogWindows: Failed to load ‘VtuneApi.dll’ (GetLastError=126)
LogWindows: File ‘VtuneApi.dll’ does not exist
LogWindows: Failed to load ‘VtuneApi32e.dll’ (GetLastError=126)
LogWindows: File ‘VtuneApi32e.dll’ does not exist
LogWindows: Started CrashReportClient (pid=55756)
LogConsoleResponse: Display: Failed to find resolution value strings in scalability ini. Falling back to default.

Things I’ve tried so far:

  1. Copying the project from a 4.27 source
  2. Copying the project from a 5.0EA source
  3. Copying the project from a 4.26 source
  4. Disabling all plugins, one-by-one (I’m using DLSS, Quixel Bridge, and in some instances FSR)
  5. Deleting all temp files from engine
  6. Deleting all temp files from project

I’m not sure what to try at this point. Anybody got any ideas what could be causing this? - Thanks

2

Id love to know that as well!

3

I’m having this same problem. I’m trying to use the Grapple Component from the marketplace. The developer is able to open and use the blueprints/level, but I cannot in P2. It works up to EA for me. I tried on a different computer as well and had the same issues.

4

[SOLUTION]

Quick update - I’ve whittled it down to one specific blueprint which is my player character. If I remove that BP using windows explorer I can launch the project and all maps and blueprints will now open (of course there are now many missing references).

I assume it’s probably a reference issue somewhere within the script of that class; I did try migrating that same blueprint with all scripts, functions and macros removed but no luck. In my case the only solution seems to be to rewrite this specific blueprint and correct all the now broken references. This is a pretty manual solution but it will at least work (it’s a shame it’s such a large BP though!).

Hope that helps some others!