I've had numerous random issues with a particular vellum solver node like exploding sims and gpu error messages. In the end the solution was to simply create a new solver node and manually copying all the parameters in place. I didn't change anything in the parameters as I've preciously had made several successful sims with the particular settings. So to avoid similar issues in the future I'm trying to come to some kind of conclusion about this.. First of all I copied/pasted the solver node from another scene file. Was that perhaps the issue / or is copy/pasting nodes like that generally not recommended? Or could it be that the solver node was made with another Houdini version at some point in time , bringing in compatibility issues? Or any other ideas how the node could get corrupted?

Vellum solver has a dive target, meaning you can dive inside to further customize the simulation with microsolvers even without unlocking it

So maybe the node you copied contained some nodes inside that were causing the issues?

Ive had a closer look and theres nothing custom , just a standard vellum solver. Ive tried to copy a working vellum solver node currently living in the same SOP network and...same issue. Opencl issues, crashes etc, sim goes nuts... The terminal spits out continous "OpenCL Exception: clBuildProgram (-9999)" and other GPU related messages. However, I think I got it working by switching from "minimal" to "full mode" and back again, as I said, I think... but Im not sure what actually makes it work or fail, alittle frustrating as it takes some time everytime I need to copy it.