Losing USB Device each time EX2Ultra reboots

Each time of late that the OS5 firmware has been automatically installed and the NAS reboots, the attached USB drive interface reports a failure and the drive fails to remount. This has only recently started occurring since the last two or three firmware updates. I keep an equally sized USB drive attached as an extra backup drive for the NAS (better to be safe in my experience). This would appear to be a firmware fault as updates didn’t affect it prior to the recent releases. Can anyone suggest a workaround or fix for this problem?

Does this issue occur with a simple reboot of the My Cloud EX2 Ultra without a firmware update?
If yes, can you duplicate the issue, collect the system logs and send to support along with the following information make, model, capacity and format of the external USB drive and let me know the case number?

How to Collect My Cloud System Logs

Answer ID 18374