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What's wrong with these ones? They very rarely need to be replaced.If they actually do, you're probably best to get some standard 4-screw ones and drill the extra holes.
Do you notice them slipping, if you fit the strings with a nice tight even wrap of 2-3 turns on the post, and only tune up to the note?
Nothing wrong with them then.Just check the screws are tight and if necessary put a little grease (standard white lithium grease is fine, or vaseline if you don't have any) in the gears and there won't be a problem.For them to slip, the teeth or the worm gear would actually have to be worn out, otherwise there is no way they can turn backwards under the string tension.