I hope you have found the reading of the afore linked threads helpful. They give many solutions. Here is something that has helped me with electronic contacts that are simply old and not functioning as they should; Detoxit5 is the best cleaning solution to contacts I have found. You spray it into any opening you can find on a switch or potentiometer, spin the pot or open close the switch while it is wet and give it a minute to dry. Works really well. Here is a link at ebay; deoxit5