I think this is common issue with FH machines? I have a mate's one here whilst he is overseas and it is very difficult to get working properly.
If you move the machine, it can be a problem as the game was level in one room and if the other room is not level then the cabinet can slightly distort, moving the alignment of the plunger. The playfield sits in the the lock down bar mechanism and there's enough "play" to mis align the plunger.
