Is there a mod that corrects dormies walking around in the "hide" state?
Nope -- that's an occasional and random bug that just pops up now and then. It seems to happen most when they go into their room and then turn around and come right back out; seems like the 'invisible dorm' controller lags behinds. I had it happen with two or three dormies at once on occasion. It usually clears up when they leave the lot for class, or go back into their room for a longer stretch.