I've found it's very easy to get stuff reversed or backwards. I just supervised my daughter's first kit-build (SX3) and we got her front yokes swapped (left on right and vice versa) and also had her rear eccentric hubs (which control belt tension) messed up... had the tension loose on one side and tight on the other. Thanks to the help of others here on rctech, we got it fixed before we ran the car. Nothing like messing things up to teach you how to get it right the next time.