Heck, I have a bolt-on stab on one of my planes that, no matter what I do to straighten it out (shims, whatever) it ends up being misaligned. And, it flys just fine. Dispite that misalignment, it will loop just fine and roll with the best of the trainers (which isn't very well.. given it's a trainer).

I had an arf that I was putting together a few years back that when I epoxied the horizontal stab down, it was just fine. So, I set the thing up on a stand, made sure it was level, and that the epoxy had partially set up, then went to bed. When I got up the next morning, much to my surprise, the horizontal stab was canted to one side, lower on the left than on the right. I also noticed that there was a cat-paw image on one side, the side that was lower, of course. During the curing process, the cat had obviously either walked on it or put her paw on it, and just sat there. This cat has a habit of sitting in strange positions, usually with her butt on the ground and her front paws up on something. Well, it was enough, I guess, to cause the not-so-completely set up epoxy to flex a bit before finally setting up permanantly. The plane flew just fine.

Since RCKen suggested checking the receiver, I won't rehash that suggestion.