Crash 5.3 at AnimSequenceHelpers.cpp Line: 45

Hello,

Our project was working fine in UE 5.1.1, and we’ve tried to upgrade to 5.2, and now 5.3. But after transitioning to the new engine and booting the project, it always crashes out the editor and fails on the following error. Has anyone seen anything like this before? We’re at a complete loss on how to fix this or even what is happening. We are using MetaHumans if that helps.

Full crash is below:

LoginId:b9dfce30401d2fb40fc318b1f8f9c2b2
EpicAccountId:d749c06dd0e342eca0f94d9b181aebea

Assertion failed: Model [File:D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\Animation\AnimSequenceHelpers.cpp] [Line: 45]

UnrealEditor_MeshBoneReduction
UnrealEditor_MeshBoneReduction
UnrealEditor_MeshUtilities
UnrealEditor_MeshBuilder
UnrealEditor_MeshBuilder
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Core
UnrealEditor_Engine
UnrealEditor
UnrealEditor
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
kernel32
ntdll

For anyone hitting this same issue, I ended up building the source, going to that file, and commenting out everywhere it used the model variable. Re-built, and as far as I can tell, everything is fine in-game. So it must not have been critical.