CEN has 10kg servos with metal gears which are available from your local CEN dealer. As with ALL standard servos which have plastic gears, hitting objects or landing with the wheels in a position that will apply pressure to the servo can eat teeth. Send your problem servo to

CEN/GTC
Customer Service
1800 E Miraloma Ave. Suite F
Placentia, CA. 92870

Discribe what the problem is, and if they determine that the problem was with the servo, they will warranty it. I personally use the CEN 10kg servo for throttle and break, and aftermarket for steering, but hey I race a Genesis.