Reply to Browse knob jumps

hey guys..

after heavy usage of the s4 since i bought it when it came out, my browse knob often skips, jumps over a track or doesnt move the highlited area at all..
sometimes the loop length knob does this in browse mode too..

is there a possibility of removing the fader cap? i tried, but didnt want to apply too much force..

or will cleaning the underneath with some canned air do the trick?

thanks for your help.
wp