It may not be a case of the kill switch failing. Sometimes, in some installations, the kill switch will allow the ignition Rf noise to be transmitted back to the receiver, causing interference like problems. I'm not familira with your particular switch. Just check it to make sure it is installed properly. Also, I know early Hitec 2.4 receivers had issues with kill switches, they correcetd with a software update.

If elimatimng or disconnection the switch corrects the problem, then you know it was either the switch or the installation. since you indicate you didn't have the problem until you installed the kill switch, it only makes sense it is one or the other.