I have enabled pause tick for all components of an Actor ( UActorComponent::SetTickableWhenPaused and AActor::SetTickableWhenPaused ).
Now when I pause the game (APlayerController::SetPause) editor crashes with the following trace:
> UE4Editor-Engine.dll!operator new<TRefCountPtr<FGraphEvent>,TInlineAllocator<4,FDefaultAllocator> >(unsigned __int64 Size, TArray<TRefCountPtr<FGraphEvent>,TInlineAllocator<4,FDefaultAllocator> > & Array) Line 2656 C++
UE4Editor-Engine.dll!FGraphEvent::DontCompleteUntil(TRefCountPtr<FGraphEvent> EventToWaitFor) Line 387 C++
UE4Editor-Engine.dll!USkeletalMeshComponent::RefreshBoneTransforms(FActorComponentTickFunction * TickFunction) Line 1104 C++
UE4Editor-Engine.dll!USkinnedMeshComponent::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction * ThisTickFunction) Line 459 C++
UE4Editor-Engine.dll!USkeletalMeshComponent::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction * ThisTickFunction) Line 618 C++
UE4Editor-Engine.dll!UActorComponent::ConditionalTickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction & ThisTickFunction) Line 1108 C++
UE4Editor-Engine.dll!FActorComponentTickFunction::ExecuteTick(float DeltaTime, ELevelTick TickType, ENamedThreads::Type CurrentThread, const TRefCountPtr<FGraphEvent> & MyCompletionGraphEvent) Line 656 C++
UE4Editor-Engine.dll!FTickTaskLevel::RunPauseFrame(const FTickContext & InContext) Line 432 C++
UE4Editor-Engine.dll!FTickTaskManager::RunPauseFrame(UWorld * InWorld, float InDeltaSeconds, ELevelTick InTickType) Line 627 C++
UE4Editor-Engine.dll!UWorld::Tick(ELevelTick TickType, float DeltaSeconds) Line 1202 C++
UE4Editor-UnrealEd.dll!UEditorEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 1339 C++
UE4Editor-UnrealEd.dll!UUnrealEdEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 366 C++
UE4Editor.exe!FEngineLoop::Tick() Line 2359 C++
UE4Editor.exe!GuardedMain(const wchar_t * CmdLine, HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, int nCmdShow) Line 142 C++
UE4Editor.exe!WinMain(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * __formal, int nCmdShow) Line 189 C++
Quick debug shows that TickFunction passed to USkeletalMeshComponent::RefreshBoneTransforms has no CompletionHandle when calling this line (SkeletalMeshComponent.cpp line 1104):
TickFunction->GetCompletionHandle()->DontCompleteUntil(TickCompletionEvent);
The bug can be reproduced with simple SkeletalMeshActor by placing it in the world with pause tick set up and pausing the game.