I've seen very few actual rifle problems. I had a Rem 700 trigger freeze up once, and I've seen factory ammo that was over pressure lock up a bolt once although that was at the range. But as others have said, any problems were almost always user error.

I've fallen with my rifle a couple of times while hunting in the mountains and felt I had to recheck zero, but the scopes (in these cases Leupold Vari X-III's) did not change zero.