It has been over 20 years since I've seen one of those, but--IIRC--those different presets are potentiometers that control a varactor array in the front end to tune the circuits. If those pots or their corresponding switches are dirty the system won't work well at all. I used to use Tun-O-Wash (Very safe on plastics, but thanks to the Montreal Protocol now NLA
) to clean them up, followed by a preservative/lubricant. After the carrier dried I'd then do the peaking and tweaking.