MPK25 question

I've had hand-me-down MPK25 for a number of years now. I use it in FLStudio and functionally, it's 100% perfect.

Since day 1 the bank of knobs on the top right of the keyboard have never had the same amount of tension. Some knobs turn very easily while others need more force.

Is this normal on anyone else's mpk25 or 49?

Pull the knobcovers off,Spray some electrocleaner and wipe'em with qtip.
Worked for me.