It was user error - so dumb, it made me laugh at myself. I had turned on the two transmitters, one at a time, checked them with the receiver, programmed them in, then began to turn them off (or so i thought) with my Marshall signal tester/mag switch. When i got to the second transmitter, it APPEARED to be malfunctioning (switching between single-beep/double-beep) because i had not held the magnet on the first transmitter long enough to turn it off. So, the first transmitter (4 ft. Away) was still beeping. Since the signal tester functions as a mini-receiver and picks up/reads all bands, it was continuously reading the single-beep from the first transmitter. So, when I tapped the seconnd transmitter "on" i got a false double-beep from the combined signals of the two transmitters. When I tapped it "off", I still got a false single beep from the other transmitter (which I did not realize was still turned on, LOL).

Morals of the story?
1. Slow down; think dummy!
2. When using multiple transmitters in the same proximity, use the receiver (not just the signal tester) to verify each transmitter.

Thought I'd share my "Duh!" moment so y'all could cuckle at the telemetry rookie.