Welcome Tim, the recoil your refer to is this the tank recoil? As you fire the tank jerks back? If so this is triggered from a limit switch connected to the gun.
Sounds like you have some internal wiring issues, we can help but the tank will need to be partially disassembled. The wiring schematic section has an older schematic of the RX18. Using this as a guide you can check the firing circuit and determine the limit switch wires as they will be absent from the older schematic.
The distance could be the transmitter,but most likely it is the internal receiver connection to the antennae. Do you loose all functions or just driving control?
If your willing to provide some information I'm sure we can help you with these issues.
Where did you purchase this tank? Tankzone UK has a section of instructional directions for repairing your tank,here is the link.
http://www.tankzone.co.uk/category/man_henglong.htm" onclick="window.open(this.href);return false;
cheers Saxondog