Not sure what has happened here but worth a note of caution;
Those pots are quite delicate, the weak link is those tiny rivets that hold the lugs. The connection between lugs and pads is only via contact pressure of rivet so just bending those solder lugs can make the connection intermittent and as mentioned overheating will weaken the rivet pressure on the joint.
If the lug can be moved from side to side then the rivet has lost it's grip and a high chance you will have trouble. I've revived a few simply by repressing the rivets. (Delicately of course)
If the pot is just scratchy then that is the pad to wiper connection failing or dirty, cleaner may help for a while but I've found if you have it apart you may as well replace it.
FWIW, I wrap a short piece of masking tape around the outside of the back cover which helps to keep blobs of solder and crap out of the working internal parts.
It also stops small insect critters from setting up house,,, you would be surprised where critters find homes
Hope it helps, Phil.