I just changed servos on both trucks, cleaned and oil the bearings. Put a hot racing servo mount on my Kraton. The Kraton has popped the a-arm ball out 3 times. The trucks were jumping around 7ft high. My sons granite was going higher, crashing backflips and every way you can imagine, plus the abuse of an 8 yr old. The granite is tough. This is my 3rd time running this brand new Kraton. It landed solid slightly more towards the back wheels, I wasn’t going fast, jumped a distance of maybe 10ft. I’m disappointed with it so far. What upgrades should I buy?