Sequencer crash (access violation)

Hello everyone,

We are trying to finish up our small project and we need to record two vehicles to create a sequence for the end product. But since lately we get a random access violation error/crash. I have specified that it comes from the other vehicle only. Nothing on the internet we found helped (deleting intermediate folder and appdata content etc). We are using blueprints atm and dunno how to use VS to identify the problem while recording a sequence. Thou I believe it has to do with some NULL calling in the blueprints but without proper debugging it is hard to identify. Any advice or link to a tutorial etc would be really appreciated. I can provide more details and info if needed. Here is the error:

Access violation - code c0000005 (first/second chance not available)

UE4Editor_MovieScene!UMovieSceneSection::GetChannelProxy() [d:\build++ue4\sync\engine\source\runtime\moviescene\private\moviescenesection.cpp:138]
UE4Editor_SequenceRecorder!FMovieScene3DTransformSectionRecorder::FinalizeSection() [d:\build++ue4\sync\engine\source\editor\sequencerecorder\private\sections\moviescene3dtransformsectionrecorder.cpp:220]
UE4Editor_SequenceRecorder!UActorRecording::StopRecording() [d:\build++ue4\sync\engine\source\editor\sequencerecorder\private\actorrecording.cpp:720]
UE4Editor_SequenceRecorder!FSequenceRecorder::StopRecording() [d:\build++ue4\sync\engine\source\editor\sequencerecorder\private\sequencerecorder.cpp:921]
UE4Editor_SequenceRecorder!TBaseSPMethodDelegateInstance<0,SSequenceRecorder,0,void __cdecl(void)>::ExecuteIfSafe() [d:\build++ue4\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:345]
UE4Editor_Slate!FUICommandList::ExecuteAction() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:97]
UE4Editor_Slate!SToolBarButtonBlock::OnClicked() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\multibox\stoolbarbuttonblock.cpp:300]
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,0,FReply __cdecl(void)>::Execute() [d:\build++ue4\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:269]
UE4Editor_Slate!SButton::OnMouseButtonUp() [d:\build++ue4\sync\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:290]
UE4Editor_Slate!FEventRouter::Route >() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:268]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5472]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5979]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [d:\build++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5959]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [d:\build++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1736]
UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() [d:\build++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2182]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() [d:\build++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:895]
UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() [d:\build++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:732]
user32
user32
UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() [d:\build++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:129]
UE4Editor!FEngineLoop::Tick() [d:\build++ue4\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3417]
UE4Editor!GuardedMain() [d:\build++ue4\sync\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\build++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:144]
UE4Editor!WinMain() [d:\build++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:223]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:283]
kernel32
ntdll

I believe that’s a bug that’s fixed in 4.21. If you compile from source, you can grab this CL#4089180.