I'd check everything like MJAsony said. A few strange ones I have seen are metal to metal contact somewhere causing radio interferance when its running only. I have had a throttle servo go wide open only when the engine is running. Something inside the servo causes this glitch when the engine is running. Or just the reciever is bad period. Those are some of the odd issues that are harder to trace. I hate when it has to be running to get the glitch to wide open throttle. Makes it very difficult to trace the issue.