Trevor:
If you go to
Menu >> Settings >> System >> Signal Detection you will find all your currently tuned multiplexes (channel numbers) are listed to pick from. There should be six or so. If you tell us what they are we can check whether they are correct and all from one transmitter.
Check out
Things Every... (click) section 2, which will direct you to exact and detailed instructions how to go about a manual tune if you wish to do that. Standard firmware 1.02.32 does a better job than previous firmwares of automatic tunes.