This is the first time I have EVER heard of a V2 gearbox failing, and I have literally installed dozens of those things. What happened on yours is probably a one-in-a-million event, so I would replace it with the exact same gearboxes that were in there. I've tried the V3 and I don't like them, and with a Leo they won't give you the scale speed that you're after. Since it was a taigen tank, I would contact Erik and tell him what happened, I think at the very least he'll offer you a replacement set at a discount. He might even want to see your old ones in order to determine what went wrong. That's very, very rare and like I said, this is the first set that I've ever heard of that has failed.