I deleted all the drivers hvciscan identified (mostly for a Logitech webcam I use, but also one which is used to download videos (jaksta)
After all this, hvciscan said no drivers were found as non compliant.
The update still fails with the same code as before
0xc1900101 - 0x20017 failed in safe_os during boot
That's the first boot. HvSCiScan comes in on the 0xx40017 errors on the second boot. 20017 errors are related to duff drivers which you can introduce yourself. So you need to get past that. I was originally past that till a duff one got introdused by updating them. If you have a record of your original drivers you revert back. I did manage to find the first boot error looking at the log files and Googling and found reports of the one I had not working reported in the Insider program.