Weirdest mechanical failures you've ever had?

Modders tend to have some weird reliability issues with their projects since we're taking the blasters we're modding and turning them up to 11. However, what is the absolute weirdest mechanical problem you've ever experienced?

In my case, I just had my Rapidpistol fail when the pusher bumped the lip of a magazine. I cracked the epoxy on the ass end and looked at the problem. Apparently the section of the pusher mechanism that holds the 130 motor broke, so now, when the pusher gets too much force against it, the motor flies in the opposite direction of the gears that move the pusher and send it slamming out of alignment with the shell, making the pusher stop working.