Another suggestion , re the "pop bumper hit and coil stays on" .. this is most likely a switch out of adjustment (closed when it should be open , or vice versa) .. also check that when the game is in play and the score motor runs, that it always returns to the home position (ie turns full 360 degrees before stopping) .. i have been stupidly caught out by this before. If score motor doesn't return to home position then the score motor "home position" switch is either dirty or out of adjustment.
