Goldpick
Chris Johnson
From what I have read, the cz21 comes with a rubber washer only on one side and plastic on the other. Some have tried to add another washer, though it tends to put too much pressure on the coil ears, leading to breakages. Seems to be common to convert them to Anderson shaft type setups from the get go. So sounds like an inherent issue with this particular detector.
http://www.treasurenet.com/forums/fisher-research-labs/453325-cz21-wobbly-shaft-fix.html
http://www.treasurenet.com/forums/fisher-research-labs/453325-cz21-wobbly-shaft-fix.html