I picked up an x-men that had this same problem, and tried a couple different things. At first the extra velcro (I actually used a cabinet door bumper, but same idea) underneath seemed to help a lot, but then it started acting up again. I tried taking it apart and cleaning all the moving pieces, but that actually made it worse, probably because it went together again a bit out of alignment. What finally has seemed to fix it was a combination of two things. First, I made sure that both of the auto-plunger arms were touching the ball when it rests at the bottom of the shooter lane. Second, I tried to adjust the arms to make sure that when the ball rolls down the shooter lane to rest against the auto-plunger it doesn't move the arms around at all. As others have mentioned, there is a bit of play in the bushings, so if things are off center it seems like the ball will cause the arms to go out of alignment. I didn't get this perfect since the arms still shift a very slight bit when the ball hits them, but it seems to be good enough. Hopefully this will help out others who are fighting with this issue.