I just brought my project from 5.4 to 5.5 and have one blueprint class which is suddenly giving me errors. Looks like this:
Looks like a few references to classes are broken, so I go through and fix them:
No more compilation errors, everything seems. Fine.
But then I save, close, and reopen the engine and the compilation errors return, exactly how they were before. Telling me the same thing about PLACEHOLDER-CLASS and broken struct references.
Sometimes the engine will crash right as I close it, I have included the crash log:
Robomango.log (268.8 KB)
Seems to be something to do with this section but I’m not sure what to do about it:
[2026.02.10-06.04.17:426][495]AssetCheck: /Game/JacksonsBlueprints/Dungeons/MysteryDungeon/MoveTest/AC_Dungeons Validating asset
[2026.02.10-06.04.25:900][442]LogBlueprint: Warning: [AssetLog] C:\Unreal Engine\Robomango-5.5\Content\JacksonsBlueprints\Dungeons\MysteryDungeon\MoveTest\AC_Dungeons.uasset: [Compiler] Input pin Instigator specifying non-default value no longer exists on node SpawnActor PLACEHOLDER-CLASS BP Death Zone Renamed C 0 . Please refresh node or reset pin to default value to remove pin.
[2026.02.10-06.04.25:901][442]LogBlueprint: Error: [AssetLog] C:\Unreal Engine\Robomango-5.5\Content\JacksonsBlueprints\Dungeons\MysteryDungeon\MoveTest\AC_Dungeons.uasset: [Compiler] Can’t connect pins BP Death Zone and Object : PLACEHOLDER-CLASS BP Death Zone Renamed C 0 Object Reference is not compatible with Object Reference.
[2026.02.10-06.04.25:901][442]LogBlueprint: Error: [AssetLog] C:\Unreal Engine\Robomango-5.5\Content\JacksonsBlueprints\Dungeons\MysteryDungeon\MoveTest\AC_Dungeons.uasset: [Compiler] Can’t connect pins Object and BP Death Zone : Object Reference is not compatible with PLACEHOLDER-CLASS BP Death Zone Renamed C 0 Object Reference.
[2026.02.10-06.04.25:966][442]LogUObjectHash: Compacting FUObjectHashTables data took 1.76ms
[2026.02.10-06.04.34:589][415]LogBlueprint: Error: [AssetLog] C:\Unreal Engine\Robomango-5.5\Content\JacksonsBlueprints\Dungeons\MysteryDungeon\MoveTest\AC_Dungeons.uasset: [Compiler] Can’t connect pins BP Death Zone and Object : PLACEHOLDER-CLASS BP Death Zone Renamed C 0 Object Reference is not compatible with Object Reference.
[2026.02.10-06.04.34:589][415]LogBlueprint: Error: [AssetLog] C:\Unreal Engine\Robomango-5.5\Content\JacksonsBlueprints\Dungeons\MysteryDungeon\MoveTest\AC_Dungeons.uasset: [Compiler] Can’t connect pins Object and BP Death Zone : Object Reference is not compatible with PLACEHOLDER-CLASS BP Death Zone Renamed C 0 Object Reference.
Cheers for any help or suggestions!
Edit: More info: Adding references to new classes (i.e. via a new spawn actor node) also causes those references to break upon restart. Seems like something is corrupt with the blueprint as a whole that causes all the references to break whenever the engine is restarted. Anything that was a reference to another blueprint is replaced by PLACEHOLDER-CLASS.
