Glad that you found the solution!
The strange part is that in the task manager on the Target, the USB HDD never gets near 100% disk activity.
Have you checked that computer’s USB controllers support UASP?
It would be nice if B&R had a way to verify tapes. Is there any chance you guys could create a feature request to verify file to tape backups?
Yes, we have this request noted, however it has a low priority - hardware libraries verify the data on a block level during write operations, so frankly speaking tape backup is always verified. I am not sure backup VTL, though. I guess it depends on the vendor’s implementation.