7-speed RSX brake/shift lever slipping
I have a well-used Trek 520 that still has the original 7-speed RSX brake/shift levers. The right-side lever sometimes doesn't catch on the downshift action unless I put a little pressure on the lever in the braking direction or otherwise wiggle it around. It's an intermittent problem, though the lever did fail to downshift at all during a cold snap we had here a week ago. As soon as the temperature got above freezing, the lever began to work again. Is this a problem that can be solved by any cleaning or adjustment, or is this what can be expected when combo levers begin to wear out? I have a set of bar-ends that I can install, but it seems a waste of good bike parts if the combo levers can be made to work properly again. I don't have any experience with servicing these levers, so any thoughts or advice would be much appreciated.