For the last few months my MIDI controller keyboard had been developing a dodgy modwheel - it worked fine from about half way up its travel, giving me smooth and gradual MIDI output However, in the first part of its travel it not only glitched but had become dirty enough for the pot's wiper to disconnect itself from the track and give intermittent full value glitches.
Even moving it anywhere in the bottom half of its travel and leaving it there finally resulted in glitching when playing the keyboard, simply due to the vibration.
Opening up the keyboard proved not be the nightmare I was envisaging (only about a dozen screws to remove in all) and a quick squirt of DeOxit followed by a few moves back and forth over the full travel of the modwheel helped a great deal.
However, after leaving the excess DeOxit to evaporate I was still left with the occasional crackle, so I applied another squirt and wiggle (love these technical terms!) and this cured the problem completely.
In all it only took me about twenty minutes, and you can see the before/after results of recording a steady modwheel move from minimum to maximum in the screenshot below (before on the left, and after on the right):
Notice in the left hand 'before' image the spiky noise generated by the dirt, and the big missing chunk of MIDI data in the lower part of its travel, compared with the comparatively smooth curve of the 'after' image on the right.
The moral of this tale is not to put up with noisy pots until they get really aggravating - a little squirt can sometimes work wonders!