GPU Passthrough stops working after a while

Just to update this, I tired a whole new VM this time and same result, VM starts, but black screen.  No errors in VM log.  I'm seeing some unusual errors in the system log around PCIe, so am going to try a memory test as a first step,  Hopefully not another stick gone, this is expensive memory!

So starting with memory, there appears not to be any issues there.  However, I've clearly not let it run overnight, which technically I probably should do.

 

However, the one thing I didn't do, which I should have done was a full power off of the machine, resetting the hardware.  Which I've now done and now the GPU works.

 

I don't know why this is now happening, it could be a symptom of my hardware, or it could be triggered by something new in unraid.

 

The logs are there if anyone wants to look at it.  I'll log another ticket if it comes back (or try reopening this one).  Until then I guess we can close this.