Motor runs fine when I push the machine forward but cuts out when I pull the machine back
Where the handle goes into the body there will be a small crack inside there. You'll be hard pressed to find it. What it does is when you pull the machine back, the crack opens causing the socket to loosen and the electrical connections lose contact. Push forward and they make contact again.
With this fault, people seem to think its the locking lever that holds the handle in; it isn't.
Play around with that and see, if it is that, a replacement main rear body is required.