If your spark plug cap comes loose or the ignition has an internal short and grounds out it can cause interference. Doesnt matter what brand or frequency protocal you are using. If you use metal pushrods it can amplify a problem as it can bring the noise closer to the servo and then it has a nice transmission path into the receiver. If you use the same battery to power both the ignition and reciever, the common ground can make it worse.. Lots of guys use all metal pushrods and havent had problems. Pay your money take your chances.