I do nott know well why this happens often.
So I added a message that disappeared when crashed.
Fatal error!
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffff
UE4Editor-Kismet.dll!SBlueprintEditorSelectedDebugObjectWidget::GenerateDebugObjectNames() (0x00007ffe384d1cc3) + 0 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\sblueprinteditorselecteddebugobjectwidget.cpp:403]
UE4Editor-Kismet.dll!SBlueprintEditorSelectedDebugObjectWidget::Construct() (0x00007ffe384a068e) + 0 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\sblueprinteditorselecteddebugobjectwidget.cpp:39]
UE4Editor-Kismet.dll!TDecl<SBlueprintEditorSelectedDebugObjectWidget,RequiredArgs::T1RequiredArgs<TSharedPtr<FBlueprintEditor,0> & __ptr64> >::operator<<=() (0x00007ffe38480e7e) + 0 bytes [c:\development\unrealengine\engine\source\runtime\slatecore\public\widgets\declarativesyntaxsupport.h:1321]
UE4Editor-Kismet.dll!FBlueprintEditorToolbar::FillDebuggingToolbar() (0x00007ffe384c9421) + 101 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\sblueprinteditortoolbar.cpp:731]
UE4Editor-Kismet.dll!TBaseSPMethodDelegateInstance_OneParam<FBlueprintEditorToolbar,void,FToolBarBuilder & __ptr64,0>::Execute() (0x00007ffe384bf174) + 11 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:161]
UE4Editor-Kismet.dll!TBaseSPMethodDelegateInstance_OneParam<FBlueprintEditorToolbar,void,FToolBarBuilder & __ptr64,0>::ExecuteIfSafe() (0x00007ffe384c30dd) + 12 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:171]
UE4Editor-Slate.dll!FExtender::Apply() (0x00007ffe45241fbc) + 0 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\framework\multibox\multiboxextender.cpp:219]
UE4Editor-Slate.dll!FToolBarBuilder::ApplyHook() (0x00007ffe45242177) + 0 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\framework\multibox\multiboxbuilder.cpp:470]
UE4Editor-Slate.dll!FToolBarBuilder::EndSection() (0x00007ffe45264e11) + 0 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\framework\multibox\multiboxbuilder.cpp:460]
UE4Editor-UnrealEd.dll!FAssetEditorToolkit::GenerateToolbar() (0x00007ffe3da02bf7) + 0 bytes [c:\development\unrealengine\engine\source\editor\unrealed\private\toolkits\asseteditortoolkit.cpp:717]
UE4Editor-UnrealEd.dll!FAssetEditorToolkit::RegenerateMenusAndToolbars() (0x00007ffe3da1387d) + 0 bytes [c:\development\unrealengine\engine\source\editor\unrealed\private\toolkits\asseteditortoolkit.cpp:780]
UE4Editor-Kismet.dll!FWorkflowCentricApplication::SetCurrentMode() (0x00007ffe3865ad61) + 9 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\workflowcentricapplication.cpp:69]
UE4Editor-Kismet.dll!FBlueprintEditor::SetCurrentMode() (0x00007ffe3840f140) + 0 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\blueprinteditor.cpp:1206]
UE4Editor-UMGEditor.dll!TBaseSPMethodDelegateInstance_OneParam<FWidgetBlueprintEditor,void,FName,0>::Execute() (0x00007ffe327e7bcb) + 34 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:161]
UE4Editor-UMGEditor.dll!TBaseSPMethodDelegateInstance_OneParam<FWidgetBlueprintEditor,void,FName,0>::ExecuteIfSafe() (0x00007ffe327ed330) + 31 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:171]
UE4Editor-Kismet.dll!SModeWidget::OnModeTabClicked() (0x00007ffe3867e169) + 0 bytes [c:\development\unrealengine\engine\source\editor\kismet\private\workfloworientedapp\smodewidget.cpp:156]
UE4Editor-Kismet.dll!TBaseSPMethodDelegateInstance_RetVal_TwoParams<SModeWidget,FReply,FGeometry const & __ptr64,FPointerEvent const & __ptr64,0>::Execute() (0x00007ffe38677a06) + 23 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:161]
UE4Editor-Slate.dll!TBaseDelegate_RetVal_TwoParams<FReply,FGeometry const & __ptr64,FPointerEvent const & __ptr64>::Execute() (0x00007ffe4519398a) + 6 bytes [c:\development\unrealengine\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:1058]
UE4Editor-Slate.dll!SBorder::OnMouseButtonDown() (0x00007ffe4532370f) + 17 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\widgets\layout\sborder.cpp:116]
UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonDownEvent() (0x00007ffe451dd8ef) + 23 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3330]
UE4Editor-Slate.dll!FSlateApplication::OnMouseDown() (0x00007ffe451caf9b) + 19 bytes [c:\development\unrealengine\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3247]
UE4Editor-Core.dll!FWindowsApplication::ProcessDeferredMessage() (0x00007ffe457b77f2) + 32 bytes [c:\development\unrealengine\engine\source\runtime\core\private\windows\windowsapplication.cpp:1284]
UE4Editor-Core.dll!FWindowsApplication::DeferMessage() (0x00007ffe457a3eab) + 74 bytes [c:\development\unrealengine\engine\source\runtime\core\private\windows\windowsapplication.cpp:1637]
UE4Editor-Core.dll!FWindowsApplication::ProcessMessage() (0x00007ffe457b8b29) + 41 bytes [c:\development\unrealengine\engine\source\runtime\core\private\windows\windowsapplication.cpp:737]
UE4Editor-Core.dll!FWindowsApplication::AppWndProc() (0x00007ffe457a07f2) + 0 bytes [c:\development\unrealengine\engine\source\runtime\core\private\windows\windowsapplication.cpp:599]
USER32.dll!UnknownFunction (0x00007ffe62aa2434) + 0 bytes [UnknownFile:0]
USER32.dll!UnknownFunction (0x00007ffe62aa2297) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FWindowsPlatformMisc::PumpMessages() (0x00007ffe457b8fe6) + 48 bytes [c:\development\unrealengine\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:757]
UE4Editor.exe!FEngineLoop::Tick() (0x00007ff672508f22) + 8 bytes [c:\development\unrealengine\engine\source\runtime\launch\private\launchengineloop.cpp:2111]
UE4Editor.exe!GuardedMain() (0x00007ff6724feb0e) + 0 bytes [c:\development\unrealengine\engine\source\runtime\launch\private\launch.cpp:133]
UE4Editor.exe!GuardedMainWrapper() (0x00007ff6724feb7a) + 5 bytes [c:\development\unrealengine\engine\source\runtime\launch\private\windows\launchwindows.cpp:125]
UE4Editor.exe!WinMain() (0x00007ff67250a6f9) + 17 bytes [c:\development\unrealengine\engine\source\runtime\launch\private\windows\launchwindows.cpp:201]
UE4Editor.exe!__tmainCRTStartup() (0x00007ff67250b629) + 21 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
KERNEL32.DLL!UnknownFunction (0x00007ffe610b16ad) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffe63064629) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffe63064629) + 0 bytes [UnknownFile:0]