Quoted from BrianBannon:

These moves can damage games. Several years ago, I replaced a set of legs on Iron Man. According to the bartender, she caught some guy sliding the game back and forth trying to save the ball. She described what she saw and it sounded like a death save to me. He had pulled the game about six inches away from the wall so he could really move it around. There was an expansion joint with a lip on it in the floor and this guy was shoving the game back and forth over the expansion joint, ended up putting a slight bend in a couple of legs. At the time, I didn't realize that was even possible. Here is the kicker, I had the game set to five balls with a generous tilt! This guy must have been a lousy player as he was nowhere to be found on a two week old high score table that still had some default scores. Bar owner told the staff if that bastard ever comes back to let him know so he can toss him out.
Another time there was a guy doing bangbacks on my EBD at Chicago Expo many years ago. He broke the weld on one of the tabs of the lockdown bar. Eight Ball Deluxe can be a real bitch sometimes, but c'mon.