Sounds like you need to make a mechanical adjustment with your servo throw so that it doesn't kill the engine. I very seriously doubt that there is something wrong with the radio. Opening up the radio and trying to "fix" it yourself will more than likely void the warrenty, and could possibly cause more problems than it fixes. Just adjust the throw on your throttle servo so it doesn't die and you'll be just fine. I am curious of one thing. Where is your throttle trim at when this is happening. Most pilots use the throttle trim to make adjustments such as this. Is your trim set all the way in one direction??

Ken