I have used many brands of transmitters and receivers over the last 30 years and, with the exception of the old AM radios on 27MHz, have never had a transmitter being close to the receiver cause glitching. A much more possible reason for the glitching is a poor connection. If the connectors (especially any extensions) have not been exercised (repeatedly connected/disconnected) recently there may be a high impedance connection due to corrosion of the contacts. Just exercise them a few times and see if the problem goes away.