I've got a problem with a couple of the wire gates on my Police Force (1989) table. The two key problem spots are the middle ramp entry gate (that causes the drum-roll to invoke) and the other is the metal gate at the top of the playfield where you shoot the right orbit and wrap around to the G.U.N./TOP COP area. I've included clarifying images of each.
Quite frequently (at a guess maybe 25% of the time overall, maybe more) a ball that is hit very cleanly into the middle ramp will get stopped dead by the metal gate. When I test it with my finger I'm unable to reproduce it, so I'm not sure what exactly is malfunctioning. It seems that the gate must be getting bound on something, maybe the ball is hitting it high or something? And instead of swinging open it just punts the ball back. The metal gate up near the top of the playfield is a similar problem but it much more pervasive. I'd say that well over half the balls that get sent up the right orbit wall get rejected by the gate. Again, it moves when probed with the finger so I'm having a hard time understanding what is happening under play conditions that makes it deny entry.
I have tried the obvious of lubricating the gate hinges with some machine oil, but it hasn't fixed the problem. Perhaps the metal gets need a slight adjustment in their shape or something, but I don't want to mess with that before I see if someone else has been through this trouble shooting process and has a hot tip on what's likely needed.