I have an Eflite mini Edge ARF, with a Park 400 inrunner and Eflite plastic gearbox. This is the power setup recommended by the instruction manual. I have stripped the plastic spur gear on three gearboxes. The total flight time on those three flights total approximately thirty seconds.

I have installed the gear boxes per the instructions, used the plastic shipping bag as a gauge between the pinion and spur gears, lubed the pinion and spur, etc. etc. I am obviously doing something wrong, but obviously I can't figure out what it is.

I would greatly appreciate any and all input regarding this problem. Thank you in advance for your assistance!