Well to my surprise, running via VLC (or equivalent) seems to have made a large difference, no timouts on a 12 hour run.

Yes I have tried, cheap cables, posh cables, USB2, USB3, Hub, no Hub, Camera Hub....

So if it keeps working I think the transfer of Main camera image which takes 20sec, is blocking the guide camera download, causing a time out then hanging the driver. Running locally on the mini pc reduces the main down load to 2 seconds.

TIme will tell,

Anyway off to dark skies next week and I hope it keeps working.

On a different tack, My new Altair GP130MM backup plan isn't working with INDI/EKOS, black images. But that's another adventure.