A console should not pick up a supplementary transmitter unless that channel is set to ON in the console's channel settings.
So the first check is to make 100% sure that ALL channels are set to OFF except, obviously, for the ones that you're expecting to receive - typically just the ISS on #1 (but you may have extra transmitters in your set-up). This wouldn't account for why an extra transmitter showed up just for a short time, unless maybe some adjustments were being made to the console at around the same time.