You most likely have a playfield switch that's closed. Check any switch that scores 100 on the playfield. They should all have a small gap. You prolly have one or more more that's closed. Also check the 100's relay in the backbox. It might be misadjusted. It's prolly one of those center stand-ups.
Do not keep playing the machine until you get the coil to stop locking on. It will start causing damage soon.