UE 5.6.1 crash when opening projects with MetaHuman - MeshUtilities / Array index out of bounds

General Issues and Bug Reporting
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1

Summary

Hello,

After updating to UE 5.6.1 I am experiencing consistent crashes when trying to open projects that use MetaHuman characters. Even old projects that worked fine before now fail on startup or when opening a Blueprint with MetaHuman.

The crash log shows:

Summary

LoginId:0dabcf4c41c4da46e99d688afabde0d0
EpicAccountId:aeeeab7ade9f4eb1ab3de83313652cbf

Assertion failed: OutTangentZ.Num() == NumWedges [File:D:\build++UE5\Sync\Engine\Source\Developer\MeshUtilities\Private\MeshUtilities.cpp] [Line: 2094]

UnrealEditor_Core
UnrealEditor_MeshUtilities
UnrealEditor_MeshUtilities
UnrealEditor_SkeletalMeshUtilitiesCommon
UnrealEditor_SkeletalMeshUtilitiesCommon
UnrealEditor_SkeletalMeshUtilitiesCommon
UnrealEditor
UnrealEditor
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
kernel32
ntdll

or

Summary

Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 1067]
Array index out of bounds: 146789216 into an array of size 192282

0x00007ffac4634028 UnrealEditor-Core.dll!UnknownFunction
0x00007ffa931fe88c UnrealEditor-MeshUtilities.dll!UnknownFunction
0x00007ffa931cc395 UnrealEditor-MeshUtilities.dll!UnknownFunction
0x00007ffb66979373 UnrealEditor-SkeletalMeshUtilitiesCommon.dll!UnknownFunction
0x00007ffb66979622 UnrealEditor-SkeletalMeshUtilitiesCommon.dll!UnknownFunction
0x00007ffb669793ae UnrealEditor-SkeletalMeshUtilitiesCommon.dll!UnknownFunction
0x00007ff763a6d773 UnrealEditor.exe!UnknownFunction
0x00007ff763a745a3 UnrealEditor.exe!UnknownFunction
0x00007ffac42fdc55 UnrealEditor-Core.dll!UnknownFunction
0x00007ffac42fdb2e UnrealEditor-Core.dll!UnknownFunction
0x00007ffac4323db1 UnrealEditor-Core.dll!UnknownFunction
0x00007ffac42e5fe5 UnrealEditor-Core.dll!UnknownFunction
0x00007ffac4501a33 UnrealEditor-Core.dll!UnknownFunction
0x00007ffac49a37cd UnrealEditor-Core.dll!UnknownFunction
0x00007ffac499c91f UnrealEditor-Core.dll!UnknownFunction
0x00007ffbe4b7e8d7 KERNEL32.DLL!UnknownFunction

Crash in runnable thread Background Worker #13

I have already tried:

  • Clearing DerivedDataCache and all Saved/Intermediate folders
  • Removing custom ConsoleVariables.ini
  • Fresh reinstall of UE 5.6.1
  • Testing both on new empty projects and migrated projects
  • Removing the whole windows system and trying to to run project on brand new windows11

The issue appears specifically when using MetaHuman assets.
On another PC with the same engine version the same assets work fine.

Any recommended fix or workaround?

Thanks in advance for your help.

UPD: Happense even with example MetaHumans project. Probably It’s on my side, but I have no idea how to solve it.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

Assets

Steps to Reproduce

  • Create rigged metahuman or open a scene with existing one
  • Crush happens

Expected Result

Working metahuman asset

Observed Result

Crush

Platform(s)

Windows