I'll start by saying if you think you have a problem, call (or email,
prosupport@vexrobotics.com) us.
We have had a few reported cases of 3:1 gear kits having seized gears or being a very tight fit in the ring gear. In most cases of a tight fitting 3:1 gear kit it's a combination of the gear kit being toward the high side of the tolerance and the anodizing on the ring gear being a little thicker. This is easily solved with a run in.
I've seen two cases of gears seizing on pins. One was from a bur on the bore of the gear. The other was from a crooked pin on the carrier. I've yet to see any cases where the pin or bore on the gear were out of tolerance.
In some reported cases we've been able to fix the issue and in others we've replaced the gear kit.
Here are a couple recommendations I have if you have a tight fitting 3:1 gear kit:
1) Make sure there's no dirt or large debris on the gear teeth.
2) Run the gearbox in, lubricated, for 30-60 minutes. All gearboxes need to be run in at some point. In some cases (ex: the transmission in your car) they do the run in at the factory. However, due to the modular nature of the VersaPlanetary we do not have that luxury. Note:
Lubricated does not mean packed full of grease. You can over lubricate a gearbox.