I'm not familiar with those motors but have you tried to lube the pivot shaft. Mine has 2 zerk fittings for this but even if yours doesn't have an,y it might help to try and get some lube in there.
There might be some corrosion inside. If this is the case, the only thing that will really help is a new cable. Penetrating oil might make it last a while longer. Look for a bend in the cable also.