One or more blueprints have been modified without being recompiled" but there is no list of offending blueprints?

[SVR33]

In 4.27, I’ve run CompileAllBlueprints through the commandlet and all blueprints compile just fine - 0 errors. Yet, every time I run PIE or simulate in the editor I get the message “One or more blueprints have been modified without being recompiled. Do you want to compile them now? Yes/No”.

Normally when you get this error, there’s a list of BP’s to look at… how can I figure out what’s going on here? Could the ‘Reinstancer’ error be the real problem?

Below are results from the CompileAllBlueprints

===================================================================================

Compiling Completed with 0 errors and 0 warnings and 0 blueprints that failed to load.

[2026.02.17-00.55.19:082][ 0]LogInit: Display:
[2026.02.17-00.55.19:082][ 0]LogInit: Display: Warning/Error Summary (Unique only)
[2026.02.17-00.55.19:082][ 0]LogInit: Display: -----------------------------------
[2026.02.17-00.55.19:082][ 0]LogInit: Display: LogOutputDevice: Error: === Handled ensure: ===
[2026.02.17-00.55.19:082][ 0]LogInit: Display: LogOutputDevice: Error:
[2026.02.17-00.55.19:083][ 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]
[2026.02.17-00.55.19:083][ 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!
[2026.02.17-00.55.19:083][ 0]LogInit: Display: LogOutputDevice: Error: Stack:
[2026.02.17-00.55.19:083][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff66e248c9 UE4Editor-UnrealEd.dll!DispatchCheckVerify<bool,<lambda_787fa22efeea56ac530ee0812261dd56> >() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Misc\AssertionMacros.h:164]
[2026.02.17-00.55.19:083][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff6663bd78 UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::MoveCDOToNewClass() [D:\Build++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Kismet2\KismetReinstanceUtilities.cpp:1763]
[2026.02.17-00.55.19:084][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff6361e3bd UE4Editor-Kismet.dll!MoveSkelCDOAside() [D:\Build++UE4\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:3028]
[2026.02.17-00.55.19:084][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff6361e501 UE4Editor-Kismet.dll!MoveSkelCDOAside() [D:\Build++UE4\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:3035]
[2026.02.17-00.55.19:084][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff635f4627 UE4Editor-Kismet.dll!FBlueprintCompilationManagerImpl::FlushCompilationQueueImpl() [D:\Build++UE4\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:909]
[2026.02.17-00.55.19:084][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff6359c02f UE4Editor-Kismet.dll!FBlueprintCompilationManagerImpl::CompileSynchronouslyImpl() [D:\Build++UE4\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:276]
[2026.02.17-00.55.19:084][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff6359bd71 UE4Editor-Kismet.dll!FBlueprintCompilationManager::CompileSynchronously() [D:\Build++UE4\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:3095]
[2026.02.17-00.55.19:086][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff666100de UE4Editor-UnrealEd.dll!FKismetEditorUtilities::CompileBlueprint() [D:\Build++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Kismet2\Kismet2.cpp:754]
[2026.02.17-00.55.19:086][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff65ec8e47 UE4Editor-UnrealEd.dll!UCompileAllBlueprintsCommandlet::CompileBlueprint() [D:\Build++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Commandlets\CompileAllBlueprintsCommandlet.cpp:315]
[2026.02.17-00.55.19:086][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff65ec2755 UE4Editor-UnrealEd.dll!UCompileAllBlueprintsCommandlet::BuildBlueprints() [D:\Build++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Commandlets\CompileAllBlueprintsCommandlet.cpp:162]
[2026.02.17-00.55.19:087][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007fff65ef7566 UE4Editor-UnrealEd.dll!UCompileAllBlueprintsCommandlet::Main() [D:\Build++UE4\Sync\Engine\Source\Editor\UnrealEd\Private\Commandlets\CompileAllBlueprintsCommandlet.cpp:40]
[2026.02.17-00.55.19:087][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff75597a02c UE4Editor-Cmd.exe!FEngineLoop::PreInitPostStartupScreen() [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:3434]
[2026.02.17-00.55.19:087][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff755970d2c UE4Editor-Cmd.exe!GuardedMain() [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:132]
[2026.02.17-00.55.19:088][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff7559710ba UE4Editor-Cmd.exe!GuardedMainWrapper() [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137]
[2026.02.17-00.55.19:088][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff7559740dd UE4Editor-Cmd.exe!LaunchWindowsStartup() [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:273]
[2026.02.17-00.55.19:088][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff755985984 UE4Editor-Cmd.exe!WinMain() [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:320]
[2026.02.17-00.55.19:088][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff7559878be UE4Editor-Cmd.exe!__scrt_common_main_seh() [d:\agent_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
[2026.02.17-00.55.19:089][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff84012e8d7 KERNEL32.DLL!UnknownFunction
[2026.02.17-00.55.19:089][ 0]LogInit: Display: LogOutputDevice: Error: [Callstack] 0x00007ff8411ec40c ntdll.dll!UnknownFunction
[2026.02.17-00.55.19:089][ 0]LogInit: Display: LogConsoleManager: Warning: Setting the console variable ‘r.Streaming.PoolSize’ with ‘SetByScalability’ was ignored as it is lower priority than the previous ‘SetByProjectSetting’. Value remains ‘8000’
[2026.02.17-00.55.19:089][ 0]LogInit: Display: LogOutputDevice: Warning:

[SupportiveEntity]

Hey there @SVR33! I’ve seen FBlueprintCompileReinstancer errors most commonly when you have some form of circular dependency in your code.

This line in particular stands out [2026.02.17-00.55.19:083][ 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!

The best way to find the culprit would be to check the full logs (under Saved/Logs) and look for the blueprints being compiled immediately before the error, as it should attempt to compile it regardless. This should point to either the parent class or child class that contains one half of the circular dependency. You will have to remove the references one way to resolve it.

However if that’s not the case, there are some other reasons this could occur such as prebuilt data or a corrupted blueprint. Thread below has some other workarounds:

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::IsReinstClas…