There are a couple of components that could cause this:
- USB Hub
- USB 2 Serial (RS232) dongle/drivers
- Hand Controller Extension Cable
Have you tried doing a run without the USB Hub and seeing if you still have the problem?
A few years back, I made the mistake of buying a Hand Controller Extension cable off of ebay… mistake on my part… it was cheaply made and caused intermitten disconnects with my mount… took me forever to figure out what it was.
I’ve also seen cheaply made USB hubs cause disconnects… i had to try 3 different hubs before I found one that works reliably with my setup.