Developer Notes

Many users have reported that disabling Real-Time Thumbnails made the engine much more stable.


This is one of the widespread D3D Hung crashes that have existed since 4.14. This particular callstack has affected around 300 users. The issue has been successfully reproduced on a home PC.

Dxdiag and log with -d3ddebug are attached

Steps to Reproduce

This crash is hardware-dependent and does not reproduce on all systems. Successfully reproduced on a home PC; 4/4 attempts.

  1. Make a new blank project with Maximum Settings or open an existing project
  2. New Level > VR-Basic (theoretically any map with some reflective assets could work)
  3. Add a Sphere Reflection Capture to the level, move it around swiftly (in 'Lit' mode) for a few seconds (~20 seconds).
  4. If you don't crash, add up to 4 more Sphere Reflection Captures, swiftly moving each one around for a few seconds as you add.

The crash seems to require a built-up strain be placed on the GPU. On my home PC, having one Reflection Sphere in the level only crashed after I had swapped out materials on assets, PIE'd, and moved around lights. If I didn't take any other prior actions, then I needed between 2 and 4 Reflection Sphere before the crash would occur.


Fatal error: [Link Removed] [Line: 176] Unreal Engine is exiting due to D3D device being lost. (Error: 0x887A0006 - 'HUNG')

UE4Editor_D3D11RHI!TerminateOnDeviceRemoved() d3d11util.cpp:176
UE4Editor_D3D11RHI!VerifyD3D11Result() d3d11util.cpp:225
UE4Editor_D3D11RHI!FD3D11DynamicRHI::RHIReadSurfaceFloatData() d3d11rendertarget.cpp:1176
UE4Editor_RHI!FRHICommandListImmediate::ReadSurfaceFloatData() rhicommandlist.h:3025
UE4Editor_Renderer!ComputeSingleAverageBrightnessFromCubemap() reflectionenvironmentcapture.cpp:316
UE4Editor_Renderer!ComputeAverageBrightness() reflectionenvironmentcapture.cpp:379
UE4Editor_Renderer!TGraphTask<`FScene::UpdateReflectionCaptureContents'::`19'::EURCMacro_FilterCommand>::ExecuteTask() taskgraphinterfaces.h:868
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() taskgraph.cpp:932
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() taskgraph.cpp:679
UE4Editor_RenderCore!RenderingThreadMain() renderingthread.cpp:320
UE4Editor_RenderCore!FRenderingThread::Run() renderingthread.cpp:454
UE4Editor_Core!FRunnableThreadWin::Run() windowsrunnablethread.cpp:74

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Affects Versions4.
CreatedJan 18, 2017
ResolvedFeb 22, 2017
UpdatedSep 16, 2019