We get the same error as well and can’t track it down. Regenerating the SLN or rerunning change engine version still fails.
1>C:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.MakeFile.Targets(44,5): error MSB3073: The command ""X:\Program Files\Epic Games\UE_5.0\Engine\Build\BatchFiles\Build.bat" ACFUltimateEditor Win64 Development -Project="X:\RabidGames\git\EndlessExperimental\ACFUltimate\ACFUltimate.uproject" -WaitMutex -FromMsBuild" exited with code 6.
1>Done building project "ACFUltimate.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
========== Elapsed 03:17.975 ==========