My Ok button does not work when trying to select an option on the head unit? The scroller still scrolls through different pages just fine and the back, home menu, and MAP buttons all work proper. Any advice on what might be wrong? Thanks for any help!

 

Replacing it might be the correct way to go. Otherwise, give the controller a liberal shot of WD 40. Suspect something was spilled on it long ago.

 

I'm going to hazard a guess here, based on seeing all the crud down inside the button assembly. Someone spilled a sugary soft drink on the console and failed to remove the sticky crud adequately. Then it follows that Sticky crud + crumbly crud = jamming. See if you can pull the **** and thoroughly clean under the **** with say, some 409 on a cue-tip, probably several.