[mikethedruid]

What lubricants have you tried on the shaft? I might recommend spraying a little P-B Blaster on the front of the shaft with the radio lying down so gravity will help it flow down into the switch. Then gently try working the shaft until it turns, re-spraying now and then, until it moves normally. Then I would use a 50-50 mixture of Marvel Mystery Oil and 10W20 motor oil for a final application, working that in the same way to keep things lubricated and free. I had to use this method on a Philco Model 66 band switch, and it worked well. No heat. No damage to the switch. That radio still works a treat more than a year later.