Do you have any other brands to try, I went through a whole lot b4 i figured out it was the pots, I ha even checked mine with a ohm meter, and they seemed stable enough, but, in the end that's what it was for me. but, im using abelton, as nantoons who is a very helpful person has shown me that the code, I was using which I believe was based on yours worked for me on the software, but not one the hardware, he just posted, some code for me on the other post on here, I believe you started that one, as well, I just did a reply, so it should be towards the top, maybe some of the code he gave me will benefit you? good luck, who would have thought this simple task would end up being so difficult.
Ive built extremely more complex projects with lcds, and composite tv output with customized "text and video", temperature controlled 110vac window fan, "night" lights using 110v ac & relays, temp,humidity,altitude,and Barometric Pressure all displayed on a lcd, digital tape measures using sonar, and another one using Ir witch can also me used as safety or proximity sensor/ switches in a production plant, Infrared heat and motion detection alarm systems, an electric tuba, a synthesizer,base and treble visual Via Led volume meters, MORE...and then these dang midi controllers, for some reason, have really been tough and compared to the others these should be a walk in the park, and for me it ended up being the dang pots, who would have thought?