One of the click wheel buttons not working

@lpirar one thing you can do is measure the switch itself. Attach the leads from your multimeter to the bottom two contacts, you should see that the switch does have some resistance, and total continuity when depressed. If the switch itself checks out okay, you may have to replace the clickwheel or at worst the logic board. Make sure that the clickwheel can make contact with the switch. Sometimes the little rubber bumpers on top of the microswitches come off and preventing proper contact.

Open

Depressed switch