Getting trouble to reverse it is due to trim setup. this happened to me on EarthQuake 8E and I found a solution which is easy.

when having the trouble to reverse the truck, I set the throttle trim slightly where truck starts moving slowly to forward. I then put the trim back a little bit where truck stops moving forward. that means at the moment I have found the Throttle trim center.

i then turn the truck off, transmitter off (Using redcat GSM-2C 2.4G) Turn on the transmitter and Truck and everything works just fine

Give it a try. its all in the throttle trim setup

Cheers

Ali