With the bolts loosened, tug lightly on the truck frame.  It should pull out.  If not, loosen the bolt a little more (maybe a quarter-turn at a time.)

It's out here, and the contact strip is sagging, since it's not supported by the truck.

You can see the sagging contact strips on the frame (top) and the truck/gear tower assembly (bottom), with the gears exposed.

Clean out the gears, removing lint or dirt by blowing. Wash the whole truck/gear tower assembly in water and dish detergent, if needed, and dry completely.

The Aero-Car gear lube is a pale blue gel, which liquefies on contact with the gears.