Jim,

Business troubles with the clients....

Maybe some liquid penetrated the seal on the butterfly shaft and made it to the wiper or resistive element of the feed back potentiometer. The element and wiper needs to be cleaned with contact cleaner on a cotton swab. Make sure you wipe it clean, and not let the cleaner evaporate. Next use a little lithium white grease to lube the wiper and resistive element. You could use some 800grit sand paper on wiper to before the lube.

Best of luck,

Martin

Martin