I repaired a lot of IBM 101 keyboards in the O'l days. Most were killed by soda pop.

Once apart an eraser works well to clean the contacts as well as washing the individual parts and drying them right away and thoroughly.

The IBM keyboards had a plastic film that acted as a circuit board. I got some liquid conductive paste somewhere that I just painted on the film and that would fix open circuit issues when the film got cracks in the runners.