What causes D3D delay?

Fatal error: [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/RenderCore/Private/RenderingThread.cpp] [Line: 853]
Rendering thread exception:
Fatal error: [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Windows/D3D11RHI/Private/D3D11Util.cpp] [Line: 198]
Unreal Engine is exiting due to D3D device being lost. (Error: 0x887A0020 - ‘INTERNAL_ERROR’)

Unhandled Exception: 0x00008000

0x00007fff5a8ca859 KERNELBASE.dll!UnknownFunction []
0x00007fff007ac166 UE4Editor-Core.dll!UnknownFunction []
0x00007fff007adc51 UE4Editor-Core.dll!UnknownFunction []
0x00007fff00562c7d UE4Editor-Core.dll!UnknownFunction []
0x00007ffef20013e9 UE4Editor-D3D11RHI.dll!UnknownFunction []
0x00007ffef2005bbf UE4Editor-D3D11RHI.dll!UnknownFunction []
0x00007ffef1fe7549 UE4Editor-D3D11RHI.dll!UnknownFunction []
0x00007ffef1fe6912 UE4Editor-D3D11RHI.dll!UnknownFunction []
0x00007ffef1ff2b9d UE4Editor-D3D11RHI.dll!UnknownFunction []
0x00007fff045cb920 UE4Editor-RHI.dll!UnknownFunction []
0x00007fff045ceff0 UE4Editor-RHI.dll!UnknownFunction []
0x00007fff045ceacf UE4Editor-RHI.dll!UnknownFunction []
0x00007fff045cfc8b UE4Editor-RHI.dll!UnknownFunction []
0x00007fff045c2162 UE4Editor-RHI.dll!UnknownFunction []
0x00007ffef1d5765a UE4Editor-SlateRHIRenderer.dll!UnknownFunction []
0x00007ffef1d4c8ac UE4Editor-SlateRHIRenderer.dll!UnknownFunction []
0x00007ffef1d5f60c UE4Editor-SlateRHIRenderer.dll!UnknownFunction []
0x00007fff00339ff2 UE4Editor-Core.dll!UnknownFunction []
0x00007fff0033a393 UE4Editor-Core.dll!UnknownFunction []
0x00007fff05875391 UE4Editor-RenderCore.dll!UnknownFunction []
0x00007fff0587e254 UE4Editor-RenderCore.dll!UnknownFunction []
0x00007fff007b32ef UE4Editor-Core.dll!UnknownFunction []
0x00007fff007b2f94 UE4Editor-Core.dll!UnknownFunction []
0x00007fff5cbc7bd4 KERNEL32.DLL!UnknownFunction []
0x00007fff5d76ced1 ntdll.dll!UnknownFunction []