Not me, but my daughter's rifle. She drew a premium buck tag the first year they were offered here in Oregon. We had been hunting for a few days, and one morning we were getting into the truck to head out. I hear, "Daddy, is this part on my scope supposed to wiggle?" Um, no, that part on your scope is not supposed to wiggle. The screw holding the rear ring to the base is completely loose. I tightened it, and we pulled off at a convenient spot to check the zero. I cannot hit a piece of notebook paper at 25 yards. I studied the mount a little more and realized that I had turned one piece a quarter turn from its intended position. I fixed that, and it was back on zero. Later that day she shot a nice 4x4 at 30 yards. You don't need a real precise zero for a 30 yard shot, but it was still a huge sense of relief to see that buck go down.
The main thing that has happened by my guns is that they have frequently not hit the target they were supposed to hit.
QQ