This is what I get everyday, dont happen always but, happen very often when switching tabs.
Fatal error! > > Unhandled Exception: > EXCEPTION_ACCESS_VIOLATION > 0x00000141c96b1d00 > > 0x00000141c96b1d00 UnknownFunction > 0x00007ffa7787ebce > UE4Editor-SlateCore.dll!SWindow::ShowWindow() > [D:\Build++UE4\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWindow.cpp:1425] > 0x00007ffa77d2b21d > UE4Editor-Slate.dll!FDockingDragOperation::OnTabWellLeft() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\FDockingDragOperation.cpp:82] > 0x00007ffa77d217bb > UE4Editor-Slate.dll!SDockingTabWell::OnDragLeave() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\SDockingTabWell.cpp:370] > 0x00007ffa77c77576 > UE4Editor-Slate.dll!FSlateApplication::RoutePointerMoveEvent() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5018] > 0x00007ffa77c60e31 > UE4Editor-Slate.dll!FSlateApplication::ProcessMouseMoveEvent() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5594] > 0x00007ffa77c5334b > UE4Editor-Slate.dll!FSlateApplication::OnMouseMove() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5518] > 0x00007ffaaba9bb24 > UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() > [D:\Build++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2216] > 0x00007ffaaba89197 > UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() > [D:\Build++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2642] > 0x00007ffaaba9e389 > UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() > [D:\Build++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:1046] > 0x00007ffaaba84310 > UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() > [D:\Build++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:878] > 0x00007ffae5efe7e8 > USER32.dll!UnknownFunction > 0x00007ffae5efe229 > USER32.dll!UnknownFunction > 0x00007ffaaba9f914 > UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() > [D:\Build++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsPlatformApplicationMisc.cpp:130] > 0x00007ff77c888848 > UE4Editor.exe!FEngineLoop::Tick() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4748] > 0x00007ff77c8a117c > UE4Editor.exe!GuardedMain() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:169] > 0x00007ff77c8a125a > UE4Editor.exe!GuardedMainWrapper() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137] > 0x00007ff77c8b52bd > UE4Editor.exe!WinMain() > [D:\Build++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:268] > 0x00007ff77c8b7fea > UE4Editor.exe!__scrt_common_main_seh() > [d:\agent_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288] > 0x00007ffae6d27034 > KERNEL32.DLL!UnknownFunction > 0x00007ffae6e62651 > ntdll.dll!UnknownFunction