hmm... the cable to the display panel seems well in place, but when reassembling the unit just now i seemed to encounter some difficulty fitting the top control button flush and true into the faceplate. after adjusting it and lining things up perfectly, all is smooth again.

perhaps it was just a physical problem, with vibrations being transmitted from the case to the switch, as opposed to anything internal electronically. we'll see when i get it back in my truck later today.