Descobri o problema, era no arquivo user.cfg
Estava usando o user.cfg assim (para ganho de desempenho e estabilidade):
GameTime.MaxVariableFPS 900
PerfOverlay.DrawFps 1
RenderDevice.Force
RenderAheadLimit 2
RenderDevice.TripleBufferingEnable 0
RenderDevice.VsyncEnable 0
PostProcess.DynamicAOEnable 0
PerfOverlay.DrawFps 1
PostProcess.DofMethod 0
PostProcess.BlurMethod 0
PostProcess.DynamicAOEnable 0
PostProcess.DynamicAOMethod 0
PostProcess.HbaoBilateralBlurCsEnable 0
Render.VSyncFlashTestEnable 0
Render.DrawScreenInfo 0
RenderDevice.ForceRenderAheadLimit 2
RenderDevice.Dx11Enable 0
RenderDevice.Dx11Dot1Enable 0
RenderDevice.Dx11Dot1RuntimeEnable 0
RenderDevice.DxDiagDriverDectectionEnable 0
RenderDevice.VSyncEnable 0
Render.VSyncFlashTestEnable 0
RenderDevice.TripleBufferingEnable 0
RenderDevice.RenderAheadLimit 2
RenderDevice.StereoConvergenceScale 0
RenderDevice.StereoSeparationScale 0
RenderDevice.StereoSoldierZoomConvergenceScale 0
WorldRender.TransparencyShadowmapsEnable 0
WorldRender.SpotLightShadowmapEnable 0
WorldRender.SpotLightShadowmapResolution 1
WorldRender.PlanarReflectionEnable 0
WorldRender.DxDeferredCsPathEnable 0
WorldRender.FxaaEnable 0
WorldRender.TAAEnable 0
WorldRender.MotionBlurEnable 0
WorldRender.MotionBlurForceOn 0
WorldRender.MotionBlurFixedShutterTime 0
WorldRender.MotionBlurMax 0
WorldRender.MotionBlurQuality 0
WorldRender.MotionBlurMaxSampleCount 0
Thread.JobThreadPriority 1
Thread.ProcessorCount 8
Thread.MaxProcessorCount 8
Thread.MinFreeProcessorCount 8
Render.DrawScreenInfo 0
PerfOverlay.DrawFps 1
RenderDevice.Force
RenderAheadLimit 2
RenderDevice.TripleBufferingEnable 0
RenderDevice.VsyncEnable 0
PostProcess.DynamicAOEnable 0
PerfOverlay.DrawFps 1
PostProcess.DofMethod 0
PostProcess.BlurMethod 0
PostProcess.DynamicAOEnable 0
PostProcess.DynamicAOMethod 0
PostProcess.HbaoBilateralBlurCsEnable 0
Render.VSyncFlashTestEnable 0
Render.DrawScreenInfo 0
RenderDevice.ForceRenderAheadLimit 2
RenderDevice.Dx11Enable 0
RenderDevice.Dx11Dot1Enable 0
RenderDevice.Dx11Dot1RuntimeEnable 0
RenderDevice.DxDiagDriverDectectionEnable 0
RenderDevice.VSyncEnable 0
Render.VSyncFlashTestEnable 0
RenderDevice.TripleBufferingEnable 0
RenderDevice.RenderAheadLimit 2
RenderDevice.StereoConvergenceScale 0
RenderDevice.StereoSeparationScale 0
RenderDevice.StereoSoldierZoomConvergenceScale 0
WorldRender.TransparencyShadowmapsEnable 0
WorldRender.SpotLightShadowmapEnable 0
WorldRender.SpotLightShadowmapResolution 1
WorldRender.PlanarReflectionEnable 0
WorldRender.DxDeferredCsPathEnable 0
WorldRender.FxaaEnable 0
WorldRender.TAAEnable 0
WorldRender.MotionBlurEnable 0
WorldRender.MotionBlurForceOn 0
WorldRender.MotionBlurFixedShutterTime 0
WorldRender.MotionBlurMax 0
WorldRender.MotionBlurQuality 0
WorldRender.MotionBlurMaxSampleCount 0
Thread.JobThreadPriority 1
Thread.ProcessorCount 8
Thread.MaxProcessorCount 8
Thread.MinFreeProcessorCount 8
Render.DrawScreenInfo 0
Por algum motivo, em alguma linha (ou mais) estava causando o problema.
Agora deixei assim e parou (e continuo tendo ganho de desempenho e estabilidade):
GameTime.Maxvariablefps 600
PerfOverlay.DrawFps 1
PostProcess.DofMethod 0
PostProcess.DynamicAOEnable 0
PostProcess.DynamicAOMethod 0
Render.VSyncFlashTestEnable 0
WorldRender.TransparencyShadowmapsEnable 0
WorldRender.SpotLightShadowmapEnable 0
WorldRender.SpotLightShadowmapResolution 1
WorldRender.PlanarReflectionEnable 0
RenderDevice.Dx11Enable 0
RenderDevice.Dx11Dot1Enable 0
RenderDevice.Dx11Dot1RuntimeEnable 0
RenderDevice.DxDiagDriverDectectionEnable 0
RenderDevice.VSyncEnable 0
RenderDevice.RenderAheadLimit 0
RenderDevice.StereoConvergenceScale 0
RenderDevice.StereoSeparationScale 0
RenderDevice.StereoSoldierZoomConvergenceScale 0
(c/ Blur em 1% no game para as confs funcionarem)
PerfOverlay.DrawFps 1
PostProcess.DofMethod 0
PostProcess.DynamicAOEnable 0
PostProcess.DynamicAOMethod 0
Render.VSyncFlashTestEnable 0
WorldRender.TransparencyShadowmapsEnable 0
WorldRender.SpotLightShadowmapEnable 0
WorldRender.SpotLightShadowmapResolution 1
WorldRender.PlanarReflectionEnable 0
RenderDevice.Dx11Enable 0
RenderDevice.Dx11Dot1Enable 0
RenderDevice.Dx11Dot1RuntimeEnable 0
RenderDevice.DxDiagDriverDectectionEnable 0
RenderDevice.VSyncEnable 0
RenderDevice.RenderAheadLimit 0
RenderDevice.StereoConvergenceScale 0
RenderDevice.StereoSeparationScale 0
RenderDevice.StereoSoldierZoomConvergenceScale 0
(c/ Blur em 1% no game para as confs funcionarem)