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Error after changing BP parent class: “OwnerClass should not be 'REINST_'!” (UE4.27)

I have multiple “Enemy” blueprints that inherit from a “CombatAI“ parent class, which in turn is a child of the default “Character” class. After reparenting “CombatAI“ to a new “CustomCharacter” class, I’m getting the error message below.

Old class hierarchy: Character > CombatAI > Enemy
New class hierarchy: Character > CustomCharacter > CombatAI > Enemy

LogOutputDevice: Error: === Handled ensure: ===
LogOutputDevice: Error: Ensure condition failed: !FBlueprintCompileReinstancer::IsReinstClass(OwnerClass) [File:D:/Build/++UE4/Sync/Engine/Source/Editor/UnrealEd/Private/Kismet2/KismetReinstanceUtilities.cpp] [Line: 1763]
LogOutputDevice: Error: OwnerClass should not be 'REINST_'! This means that a REINST class was parented to another REINST class, causing unwanted recursion!
LogOutputDevice: Error: Stack: 
LogOutputDevice: Error: [Callstack] 0x00007ffd6e1c1769 UE4Editor-UnrealEd.dll!DispatchCheckVerify<bool,<lambda_787fa22efeea56ac530ee0812261dd56> >() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Misc\AssertionMacros.h:164]
LogOutputDevice: Error: [Callstack] 0x00007ffd6d9d98e8 UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::MoveCDOToNewClass() [D:\Build\++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Kismet2\KismetReinstanceUtilities.cpp:1763]

The error pops up seemingly at random when I edit any of the blueprints. I couldn’t find any way of deliberately reproducing the error, nor isolating which blueprint exactly is causing the issue.

I made a lot of deep-reaching changes before noticing the error, which makes it difficult to undo everything. Does anyone know what this error even means and how I can fix it? Web searches are giving me nothing related to my particular issue.

I’m still struggling with this and it could mean weeks of work down the drain. If anyone can offer some help, it would be greatly appreciated!

I have similar error:

[2021.11.08-14.35.26:387][  0]LogInit: Display: LogOutputDevice: Error: === Handled ensure: ===
[2021.11.08-14.35.26:387][  0]LogInit: Display: LogOutputDevice: Error:
[2021.11.08-14.35.26:388][  0]LogInit: Display: LogOutputDevice: Error: Ensure condition failed: !FBlueprintCompileReinstancer::IsReinstClass(OwnerClass) [File:D:/Build/++UE4/Sync/Engine/Source/Editor/UnrealEd/Private/Kismet2/KismetReinstanceUtilities.cpp] [Line: 1763]
[2021.11.08-14.35.26:388][  0]LogInit: Display: LogOutputDevice: Error: OwnerClass should not be 'REINST_'! This means that a REINST class was parented to another REINST class, causing unwanted recursion!
[2021.11.08-14.35.26:389][  0]LogInit: Display: LogOutputDevice: Error: Stack:
[2021.11.08-14.35.26:389][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac9d71769 UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:390][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac95898e8 UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:390][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac840e3bd UE4Editor-Kismet.dll!UnknownFunction []
[2021.11.08-14.35.26:391][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac840e501 UE4Editor-Kismet.dll!UnknownFunction []
[2021.11.08-14.35.26:392][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac83e4627 UE4Editor-Kismet.dll!UnknownFunction []
[2021.11.08-14.35.26:392][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac838c02f UE4Editor-Kismet.dll!UnknownFunction []
[2021.11.08-14.35.26:393][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac838bd71 UE4Editor-Kismet.dll!UnknownFunction []
[2021.11.08-14.35.26:393][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac955dc4e UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:394][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac8e17e87 UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:394][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac8e11eb5 UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:395][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffac8e46036 UE4Editor-UnrealEd.dll!UnknownFunction []
[2021.11.08-14.35.26:395][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648e9a01c UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:396][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648e90d1c UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:396][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648e910aa UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:397][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648e940cd UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:397][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648ea5984 UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:398][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff648ea78be UE4Editor-Cmd.exe!UnknownFunction []
[2021.11.08-14.35.26:398][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffb2c8e7034 KERNEL32.DLL!UnknownFunction []
[2021.11.08-14.35.26:399][  0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ffb2d4c2651 ntdll.dll!UnknownFunction []

But this will appear only when I will compile all blueprints in commandline and it causing no problems in my game it seems:
Engine\Binaries\Win64\UE4Editor-Cmd.exe YourProject.uproject -run=CompileAllBlueprints

Also it is temporaly fixable by “refresh all nodes” in the blueprint and resave, but then it will show this error on a other blueprint. And if I will fix the other, error is back on the previous blueprint.

But I see there “UnknownFunction” error. I had even other “UnknownFunction” error while packaging game, crashing at some group or random files. And I fixed it by moving all these files to another fresh folder and fixed redirectors. Maybe you can try it too.

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I had even other “UnknownFunction” error while packaging game, crashing at some group or random files. And I fixed it by moving all these files to another fresh folder and fixed redirectors. Maybe you can try it too.

Thank you for the reply! I didn’t have any UnknownFunction errors so far, but I’ll try moving the files to a new folder. I’ll report back when I know if it worked.

Moving the files to a new folder unfortunately didn’t fix the issue. If anyone has any other suggestions, I’d appreciate the help!

In your BluePrint you can try Right clic → Asset Actions → Reload
After Reload do a simple modification for save the BluePrint and restart the engine

If it doesn’t work you can set the parent class to “actor” then again on the origin class.
This will reset a lot of property so you will have to note and reset the settings in Class Defaults.

Do a save of you asset before do this.