I believe you may have discovered the problem on your own. I have had to go in and simply super glue a couple of the slipping gears back in place. Once I have done that they haven't come out again. If you hear your gate making noise, all may not be lost. Let us know if that works.
I never have time to repair the two gates. Glanced at them last night. Looks like the watchman's in the way. I'll try to remove the cover vs. damaging the scenery on one and see. Might get lucky? My MTH gates are SCALE. Not sure about what the other people are seeing?