OE Radio volume issues!

Bought a used radio from another member to replace the crappy aftermarket one that came with my 02 P5. Seller said it was working when shipped (good guy no reason not to trust him) but when I installed it today the volume knob does not work. When you turn the knob no volume increases both in sound and on the screen. pushing it in will turn the radio on and off but when you turn it nothing happens. Has this happened to anyone and has anyone found a way to fix it. Please any input would be awesome. Thanks

my screen always goes out, it works in sound function to where if i push or turn anything whatever its supposed to do, it does it. But for some reason the screen always trips out and the illustrations fade away

The screen works, I can read the time and change the station and all that but turning the knob doesnt do anything sound wise or on the screen. it almost feels like it isnt clicking like the tuner knob does. is there a way to pull the whole knob assembly off and inspect/clean it?

Other than having a throwdown unit to scavenge from with other problems, scoring just the face part or the whole unit, I don't know a way around this. Doesn't seem like just a clean and go thing but good luck. I've had the oem units apart pretty far down but not to the level that you are facing with the individual knobs.