@crinrict I've updated my post to be just gnome-related and added a few additional details.
The permanent gnomes have only occurred in the Wyvrnn Dorm. I have celebrated Harvestfest in a house in the same playthrough after my first two sims graduated and the gnomes acted as they normally would and I was able to put all three in my inventory. I also celebrated a Harvestfest in the opposing college dorm (I can't recall the name) and I was able to put all three of those gnomes in my inventory, also. As far as I can tell, this may be a Wyvrnn Dorm exclusive bug.
@simvasion I wasn't aware of that! I suppose one of the gnomes could be, he's one I've never seen before and is holding what I thought was bread of some sort but could possibly be a flat surface to serve as an end table. But that still doesn't make sense in a dorm that I'm completely unable to move or interact with him to the point that he blocks access to my own bed. However, the second gnome that froze in place was a different gnome wearing an intertube.
