I have a reptile basics RHP in an AP cage and cannot for the life of me figure out how you could have a gap, but strange things happen I guess. Rotates how? I can't see the area where the RHP meets the top in your pic. When I mounted mine, I did it with the top taken off and flipped upside down on a flat table so that I could ensure it was tight and flush. I can barely even get a sheet of paper corner slid between them. Maybe try sliding it an inch or two around until you find a way it can be more flush and remount it? Def do it with top off and flipped upside down.