This is a relatively new issue, although I don't recall any recent updates that would have caused it.
When I plug in a USB stick or other device, the disk and device manager pops up twice; one is the normal one away from the edge of the screen, it goes away after about five seconds (like it should)
The second, behind it, is tucked up right against the edge of the screen and does not go away until I trigger and then minimize my application launcher.
Any ideas? I'm running Wayland because of the Maalit keyboard. Haven't tried to see if it duplicates it with X11.
Yay! Happy to help! :)