Help!....GE multiband tuner dial sticks

I purchased a GE multiband receiver back in 1984, and have hardly even used it, although it is a fine radio. Just recently I was surprised to notice that the rotary tuning knob sticks in about 3 places as it is turned. I'm amazed how this happened since I have used the set only very rarely.
The sticking tuning knob is irritating, especially on shortwave bands, because sometimes I can't listen to stations that are right on the sticking spot, due to the fact that the dial moves either right or left of the area where it sticks. I had the set apart and didn't notice any areas along the tuning string that were binding, so I'm kind of perplexed by just what might be wrong. Would appreciate any help/ideas/suggestions from forum members concerning this issue. Getting the set professionally repaired is always an option, but not much of one, because these days electronic repairs are more expensive than shelling out money for a new set.