The coil is mounted by a bolt/nut through its center. The screw comes through a hole in the bottom of the cabinet, through the center of the coil, to a plate, then the nut. The coil is very close to the switch, and it didn't have to move much to hit the switch. (about 1/4") The nut wasn't very tight, so any sudden lateral movement could've caused the problem. I'll check the amp when I get the new switch. For now, it looks like the switch is all that is needed.