I’m sharing this with the hope that my experience will prevent someone else from having a heart attack.
I dropped two files into the Finder Inbox and then went to the Global Inbox in DT to file them. When I dragged and dropped the two files into a newly created DT group, the DT database, which is on one of three partitions on a new external hard drive that I had connected just hours earlier, disappeared from the Finder and the drag and drop operation failed. After a near heart attack over the possibility that the new drive had failed (I have backups), I discovered that the USB port on my Thunderbolt 3 dock had failed. I switched the drive to a different USB port and all is good now. I’ve reached out to OWC to see what they have to say. I think this issue is the reason I’ve been experiencing intermittent improper drive shutdown messages from my computer. I may not have needed to buy a new external hard drive…