id suggest that if you have no speed control (ie, it runns flat out in one direction) it has nothing to do with a stuck relay, as this would give you full speed control, but not reverse direction. If it is either full power or off, it is a frequency generation problem, either in the electronize, or reciever. swap the 2 controllers around so the your reciever runs the other (working) channel on the problem controller. If you problem then moves to the other controller, you have a reciever problem, if it stays with the same controller you need to send the controller back to electronize. This is usually pretty cheap to fix.

best of luck Phillip.