There are several points that need to be adjusting correctly for proper operation. But also take a look at the "wiper retainer" part #B-11788. Make sure these aren't bent too much to put excessive resistance on the wiper.

I would start by maybe replacing the spring with spring #A-8737. Then also inspect the ratchet for wear as well as the armature.

As far as cleaning the circuit board goes, I have used a dab of copper/brass cleaner on a micro fiber cloth and polished it. Followed up with a very thin smear on "Super Lube".