Sometimes Alpha pot shafts will stiffen if I over tighten them. I can't say that this would be a good practice in general and try it at your own risk. I have attempted to tighten shafts by evenly pinching around with pliers. DON'T try that. I've had pots loosen after cleaning. The heavier grease gets washed out of the shaft. So if there was a way to get a heavier grease into the shaft bearing that might help. I'm thinking you could start with something like melted bees wax (because it's more sticky than others) and use a cheap syringe to inject it. If you can get it into the shaft bearing it might be quite stiff and resistant once it cooled.