In searching for this issue, every link I could find was not only old, but pointed to gvfs as the culprit (which is not installed). Here’s a pic of what’s happening:
The backups devices are my (1) USB drive, LINUX-VMS is an SSD partition; all are mounted under /media. I’m not completely convinced that this is a Nemo problem in particular; can’t remember if this happened when I ran XFCE w/Thunar.