I assume there is a service that is always running, so that when Premiere is on it looks for drives to map, and oh how it loves to map drives. I cannot figure out a way to tell Premiere “do not map a drive that I’ve connected to.”
When I eject a drive, Premiere does not disconnect from it, although the media are no longer available. If I re-start Premiere the drives are gone, and here’s the thing: if I connect to the drive again, it appears in Premiere.
I’m pretty sure there are some very detailed details here and whatever they are is causing the bizarreness you’re dealing with. I have unfortunately no further solutions. I just think its very weird how Media Browser works.