I decided to do some troubleshooting so I made a new scene with just a simple sphere and a grid made into a sweep. Before I created any materials I instantly threw down a karma node in a LOP network and changed it to XPU and it began rendering fine. I made two materials and put them on the sphere and the sweep and then suddenly it errored out the same way it did in my other scene.
I found that the material with transmission set to 1 instantly causes the error. However in my original scene I did not have any transmission materials, only MaterialX materials that used texture files for albedo, roughness, and metal.
[21:07:14] KarmaXPU: device Type:Optix ID:0 has registered a critical error [cudaErrorIllegalAddress], so will now stop functioning. Future error messages will be suppressed
[21:08:13] KarmaXPU: Unable to create CUDA context for device 0
Nvidia RTX 4090 Driver Version: 531.18
I've attached the simple scene with sphere and grid that fails and crashes the XPU render and falls back to CPU.