Great catch, I just reproduced it.
The first two channels default to E2 and F1. In order to make F1,F3,F5,F7 lineup, I tried to change E2 to F1. That would have created two F1s so it did not let me. I tried again and this time there was no validation error. SO now I was stuck with two F1s and the app kinda went haywire at that point.
First, we need to get things back to normal. the app remembers your settings (even bad ones) so change F1 to a random channel.
Now, to get the lineup you want, you have to customize the channels in such a way that you are not setting two the same. So for example, if the first two channels are E2 and F1 and you want them to be F1 and F3, first make it E2 and E3, then F1 and E3, then F3 and F3. Make sense? Kinda like a puzzle.