Flickering Potentiometer

Your potentiometers are probably logarithmic ones (Audio). MIDI controllers use linear potentiometers, for obvious reasons.

You can do the correction in software, using Analog::map(int(*fn)(int)), you just need two linear approximations of the log taper, as shown in the image above, to reverse the effect. Take a look at the map example: MIDI_controller/Ex.08.Potentiometer-Calibrate.ino at master · tttapa/MIDI_controller · GitHub

I have no idea what kind impact this will have on the noise, though.