what exflexer said about the flipper coil stops. seems like alot of these recently have been coming apart.
Saw a thread recently on the autofire for ACDC where the plunger was too high up in the coil and that was fixed by placing a little bit of rubber or bumper in between where the autolauncher bracket rests against the bottom of the playfield. Also might check the little blue plastic link to see if it's breaking.