How to diagnose hashcat progress stalling?

[serious-business]

It could even be a "this process appears to be stalled" sort of event

I did find that after hashcat has stalled, running ps shows it's in a "U+" state, meaning foreground, "uninterruptible wait".  Could this be because I'm exclusively using the GPUs?  I wonder if there's any way to flag to the OS that the process is active, and to prevent or break it out of this state.

I could try out the same task in hc on Windows on the same machine, to see if it goes any better.  Is there a particular OS that hc works best on?

In the meantime, I see v7 is out, so I'll build that and give it try.  Thanks for your help!