Clicking noise behind dash

I am beginning to hear a licking noise that lasts for several seconds after shutting the rig off. The sound is coming from behind the center dash and I believe it has something to do with turning the knob from floor heat to defrost and back to floor again.

The turning knob isn't as smooth as it once was. Anyone know what issue may be going on here? I've had trouble in the past with the air blowing from the defrost vents regardless of what setting it was on. That problem was fixed, but it seems this is related. It's a 99 XJ sport stock.

Haven't found a search that discusses this. Probably because I'm not sure what I should be searching for. Anyone know if there's a vacuum issue or maybe a faulty vent door? Would like to fix this myself if possible. Any help is appreciated as always. Thanks.

Can anyone help? Just point me in the right direction. Heat and A/C work fine and air blows from correct vents (Although sometimes I have to switch from floor to defrost and back again to get air flowing from floor and not the window.) The problem, if it is one, is when I turn the ignition off I can hear what sounds like a clicking/ticking noise behind the dash in the middle. Starts as a rapid succession of clicks and tapers off to just a few till no sound.

I want to know what's happening here. Is this a problem that will get worse? Easy fix\?, etc.? If someone can point me in the right direction, I will search and see if I can fix this myself.

Again, thanks!