This is a gearset which is used to open and close doors on a camera pod. The POS gears break after a few cycles.
The way that broken tooth larger gear has narrower teeth that looks like they're wearing to a point looks to me like the tooth spacing is off just a smidge and the pressure is wearing the teeth on that gear. Be interesting to see if two new gears just by themselves and dry feel like they're binding a little. If they are, best gears you can buy will wear out and break prematurely.
See how much thinner the teeth are on that gear the arrow points to? I wonder if they're that thin on a new one.