1. I did the exact same thing as Nokoro and had the playfield slip while raised and damaged one of the plastic glass channels under the right side rail on my machine. Removing the side rail to replace the plastic glass channel was not fun.
2. I got careless and left a plastic that I was trying to flatten in the oven just a tiny bit too long and it became a melted, shriveled mess. Had spares, but it still sucked because I had done it a couple times before without issue.
3. Every now and then the ball improperly exits the wireform above Tommy's VUK so I try to bend it back in shape for better guiding. Got a little too aggressive once and snapped a weak weld. Ended up having to take the thing to a custom Harley shop to get re-welded. It's all shiny and fixed after polishing, but you can certainly spot the re-weld if you're looking for it.