Hi, since upgrading to 5.6.1 (from 5.5.4) we’ve noticed the occasional GPU crash on Windows D3D12 that the crash logs seem to indicate is coming from “RayTracing AnyHit” where the fault description states “Executing a shader instruction caused an error. This can be caused by a microcode corruption issue or a shader compiler bug.” I’ve attached the relevant crash logs/aftermath dmp for reference. We have definitely seen it occur on Windows 11/Ryzen 7900X3D/RTX 4090 (driver 576.88), but it may occur on other hardware as well (I just haven’t got the crash logs to confirm).
As far as we can tell, the crashes seem to happen at random any time that lumen hardware raytracing is enabled. We don’t have Nanite, Megalights, or VSM enabled and it seems to happen with or without raytraced shadows on. Some other potentially relevant configuration info:
We have r.RayTracing.Geometry.NiagaraMeshes=0 as a workaround for a different RT crash
The crash was reproduced using r.Lumen.HardwareRayTracing.LightingMode=2
We also enable front layer translucency reflections (r.Lumen.TranslucencyReflections.FrontLayer.Enable=1)
Do you know of any relevant fixes in 5.7+ that we may be able to cherrypick? If not, how would you suggest we track this crash down?
Looking at the logs, and seeing the Lumen reflection passes were active, sounds like an issue we randomly saw in the Witcher demo where LumenHardwareRayTracingMaterialCHS would page fault and setting r.RayTracing.PersistentSBT=0 worked around the issue. I’ll reach out to my colleagues who worked on those but I don’t believe we ever had a reliable enough repro to identify the issue. In the meant time, if you are able to test with r.RayTracing.PersistentSBT=0 and let us know if that has any effect that would be helpful.
There’s another potentially related issue that hasn’t been fixed yet
https://issues.unrealengine.com/issue/UE-351043 Uploading of the SBT via copy queue is not guaranteed to be synced with async compute queue but only direct queue in d3d12. In the logs, it didn’t appear that Lumen reflections were running async (r.Lumen.Reflections.AsyncCompute=1), so likely not the culprit here, but could be related.
My colleague also suggested you try running with D3D12.ResidencyManagement=0 to determine if the issue might be related to residency tracking on the SBT.
I just wanted to post a reminder that Epic will be on holiday break starting next week (Dec 22, 2025) and ending Jan 5, 2026 and there will be no responses from Epic on public or private tickets, though you may receive replies from the community on public tickets.