(4.21.1) cooking fails with UAT Callstack

We migrated from 4.19 to 4.21.1. And cooking fails with this callstack, we can’t figure out what to do(which file/object is it failing on?):

PackagingResults: Error: begin: stack
for UAT PackagingResults: Error: ===
Critical error: === PackagingResults:
Error: Fatal error:
[File:D:\Build++UE4\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp]
[Line: 305] PackagingResults: Error:
Illegal call to StaticFindObject()
while serializing object data!
PackagingResults: Error: [Callstack]
0x00007ff95854a388
KERNELBASE.dll!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff927a2cd1a
UE4Editor-Core.dll!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff92780a967
UE4Editor-Core.dll!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff927740df7
UE4Editor-Core.dll!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff9288070b1
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287d1d20
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287efc17
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287ffba9
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9284f38a7
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff92846731f
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287ff833
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff928611811
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff928796ab1
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff928796e07
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9286144ec
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff92871a8b3
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287185cc
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9287182c4
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff928772f2b
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff92879ace8
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff92877e105
UE4Editor-CoreUObject.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff9150c91f6
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff914f5ec87
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff914f614b1
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff914f6cbd0
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff914dca79b
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff914dfd0bf
UE4Editor-UnrealEd.dll!UnknownFunction
PackagingResults: Error:
[Callstack] 0x00007ff6c2dded22
UE4Editor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff6c2dd5783
UE4Editor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff6c2dd59ea
UE4Editor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff6c2de48da
UE4Editor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff6c2de584e
UE4Editor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff95b193034
KERNEL32.DLL!UnknownFunction
PackagingResults: Error: [Callstack]
0x00007ff95bf91471
ntdll.dll!UnknownFunction
PackagingResults: Error: end: stack
for UAT PackagingResults: Error: Cook
failed.

+1, having the same issue

Did you fix this?