In the last week, one of my 4 external USB drives has started randomly unmounting as well, and I am not sure what to do about it. The disk in question serves as a backup disk to another disk using rsync. At least once a day, I have to log in to OMV and manually remount it. I did recently upgrade from OMV 4 to OMV 5, but I do not believe that this has anything to do with the problem, as this started happening after upgrading to OMV 4.1.30 before I jumped to OMV 5.
Prior to this, I had my server up for a long time (294 days, to be exact) and the unmounting issue had not occurred at all with in that time. The disk's SMART tests are passing and I don't hear anything physically wrong with the disk when listening to it, so I am reasonably sure that there is no problem with the disk itself. What's going on? Is there anything I can do to stop this?