I had looked at a friends car with that problem and looking a bit closer at the mechanism i found that some rustproofers just slop the stuff in without care. Remove the mechanism(not the key part, the jam part) and soak in solvent over night. Blow the part out well, gob some fresh grease in it and reinstall. Take care to mark the rods and there orientation and keep your eye on the clips.(they fly fast sometimes)Good luck !