Gate three is actually lifted by the coil in behind the pf. It is down in its normal state. There are two optos in the engine entry ramp. Those control the gates, as well as the engine vibration.

When lock is NOT lit, when the ball passes through the optos, they will trigger the coil to lift the gate. The lifting of the gate only lasts a couple of seconds. If your gate is stuck up, check to see if the coil is stuck on.

Keep in mind that the gate could just be gummed up and needing a cleaning to move freely.

If your gate is down when no game is playing, you starts a game, and gate 3 lifts when the machine puts the ball in the shooter lane, then you have an issue. Pull the glass and test the optos. In normal play when NO lock is lit, opto 1 opens gate 3 and opto 2 creates a rev sound. When lock IS lit, opto 1 closes gate 2 and starts the engine rev, and opto 2 creates the rev sound.

Oops, I misspoke. When lock IS lit, opto 1 closes gate 2 only. Opto 2 starts the engine rev and starts the rev sound.

I have to admit, I am a bit confused on what issue you are having. Is gate 3 sticking up, or is it just down and not lifting up? I am curious to know if your optos are seeing something that isn't there, and therefore not seeing the ball.