ORIGINAL: JohnW
I once produced a repeatable glitch by simply holding my TX near the RX. It only happened with one make/model of RX, but was interesting none the less. As soon as I backed off to about 5 feet, the Tx/RX worked perfectly. Both the TX and RX were operating properly otherwise as per the service center. I pushed the service center for an answer, and I got it. Long winded and technical, but in short, while everything was still within operating "specs", it was possible under the right conditions for my specific TX to interfere with my specifc RX at very close range.
Cheers!
This is likely to be due to the TX overloading the front end of the RX, I am guessing that the TX aerial was fully extended? although it would probably also happen with the antenna collapsed as well.