In the original design, the worm gear was the shear point in the event of too much force being applied, or forces being built up by other elements, such as dust and/or debris clogging the mechanism. The release of the replacement alloy worm gear was a good response, in my view, but - down the line - this may have caused wear on the handle cog that the original hard plastic worm gear wouldn't have. This is why - at the initial parts replacement stage - I'm confident in saying that the wear will only be in the worm gear, because I've only ever known this to be the case.

Ray