The title pretty much explains it all. When creating a blueprint and using a subcomponent or child within that blueprint, deleting the child actor, and then undoing while in play, causes crash.

Steps to Reproduce

1. Create a blank Blueprint Project.

2. Create 2 blueprints, BP1 and BP2.

3. Add BP2 as child actor component to BP1

4. Place BP1 into level.

5. Play once, and then stop playing.

6. Delete BP2 child from BP1.

7. Play in Editor again.

8. Without stopping playing return to BP1 editor and hit Ctrl-Z. BP2 subcomponent reappears.

9. Stop playing (crash might occured here as well).

10. Save BP1.

11. Crash


UE4Editor_MessageLog! FMessageLogListingModel::AddMessageInternal() messageloglistingmodel.cpp:70
UE4Editor_MessageLog! FMessageLogListingModel::AddMessages() messageloglistingmodel.cpp:89
UE4Editor_Core! FMessageLog::Flush() messagelog.cpp:188
UE4Editor_Core! FMessageLog::~FMessageLog() messagelog.cpp:91
UE4Editor_UnrealEd! UEditorEngine::EndPlayMap() playlevel.cpp:258
UE4Editor_UnrealEd! UEditorEngine::Tick() editor.cpp:1570
UE4Editor_UnrealEd! UUnrealEdEngine::Tick() unrealedengine.cpp:347
UE4Editor! FEngineLoop::Tick() launchengineloop.cpp:2257
UE4Editor! GuardedMain() launch.cpp:142
UE4Editor! GuardedMainWrapper() launchwindows.cpp:126
UE4Editor! WinMain() launchwindows.cpp:202

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ComponentUE - Gameplay - Blueprint
Affects Versions4.7.2
Target Fix4.12
Fix Commit2974882
Main Commit2985633
Release Commit2946590
CreatedMar 12, 2015
ResolvedMay 13, 2016
UpdatedApr 27, 2018