What normally happens is that the teeth on the small gear get chewed out by the large semi circular tooth plate. The solutions are:
1. Get a brand spanking new winder assembly --- expensive.
2. Rebuild the teeth on your existing gear --- difficult but not impossible
3. Interchange the assemblies from left to right --- less difficult
If you choose method 1 keep the old mechanism as you might need it later or maybe someone else will be able to use it. For either method 2 or 3 you will find that only half the teeth on
the sector plate are used. Therefore when you reassemble the mechanism be sure to use the good half.
Warning – when swapping the left for right, dismantle only one unit at a time so you can see how to correctly reassemble the mainspring.
‘I use another penny saving method of taking out the mechanism and
turning the handle to expose the worn teeth. I then use a hammer to reflatten the teeth. If you try it, you will regain the full teeth profile and then work some new grease into the mechanism by turning the handle
back and too, before refitting. Works for me and saves having that teeth slipping moments.’