@BotJovi35 posted in the Q&A about being allowed to glue in the inserts for the high strength gears. Glue is not allowed.
I’ve fixed these in the past:
Cut 4 rubber bands. Thread an end of the rubber band through the hole, wrap to the outside (teeth), pull it TIGHT, tie it off. Repeat until each of the square edges has a rubber band. (This is easiest with someone holding the gear, or putting it into a vise)
Tap the center insert into place. if you are having a problem, you didn’t pull the rubber band tight.
Trim excess material.
The four sections of rubber push on the center to keep it in place and keep the hole in the center of the gear. In most cases you would be able to get by with one section of rubber band, the ones I was fixing had been damaged by a team, one wasn’t enough.
If it’s really a mess (*) and you want to use it with a shaft, you can always put locking bars on both sides and screw them into place. That may push you to the point of just buying another set of gears.
(*) Team wanted to have the gear spin on the 1/4" shaft so they drilled it out. Design didn’t pan out and the gears went back into the box. /sigh