They usually get gummed up and can be cleaned with a wire brush or anything else you can find to take off the tarnish. The worst I see happen to these is the bronze/copper or whatever it is bushing on the drive unit gets worn out to the point of disappearing.
Comet makes a spray on dry lubricant. I've only ever seen it on line, no parts stores. Kinda expensive. If I remember right it's $20 for the can.
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