check the wires going from the battery pack to the reciever. if there is any bad spot, or if the plug that goes into the reciever is loose then the reciever may lose power and thats whats causing your run-aways.

also, try replacing the batteries on the buggy and in the remote. may not be the problem, but its a simple thing to try.

lastly, look at the antenna on the buggy. are there any nicks or damage to the wire?(not the plastic tube, the wires inside)