It's possible that the normally open Score Motor switches that fire the target bank reset solenoids aren't gapped properly. If the gap is too wide, the switch will close late and open early providing only an abbreviated pulse to the solenoids. I think the Score Motor switches are at positions 2C and 3B but you'll want to check your schematic to be sure.
Beware that these switches operate at 120 volts AC so you should probably adjust them with the game unplugged.
/Mark