Spur gear problem with strobe slipper

I just finshed installing my 8L/ 9920 in my Emaxx, but now every time I drive it I strip the spur gear. I know the mesh was set right, and Ive seen other cars with much more power than mine with this same set up, so I dont know what to think. The first time I thought it was because the motor mount was flexing because I forgot to put 2 of the screws in, but the second time I used those screws and it stripped even faster (after about 2 minutes of running, first time it took about 5 minutes)



This is what happened to the spur. Sorry its kinda blurry, but you can see one tooth is almost all gone, and the rest of the teeth are somewhat flat-topped.


Any help would be appreciated.