Bummer it busted on ya so fast.
That's never any fun.. That's the thing about these mass produced/low expense models.. Ya need to go over them closely, before cutting them loose.. Stuff like gear mesh and wheels being seated, screws needing loctite, etc. etc. all needs to be checked out..I can see from your pic, the spur gear mesh needs to be tighter.. As was mentioned above, it needs to be tight. As tight as you can get it, but still be able to wiggle the spur and not have the pinion move.. Here's what my mesh looks like (below) and my spurs look nearlynew still.. Good luck on the replacement parts! (Also, be warry of going to all aluminum or metal.. All that usually does is cause something further down the line to break. And usually, it's something harder to get to, or more expensive to replace.)