SOU-FRA
It's worth remembering that FlyBe dropped MAN-FRA and BHX-FRA not so long ago. The SOU flight was the only FRA route that wasn't culled. So maybe FRA as a market just isn't working for them.
The dropping of the MAN and BHX routes was quite a surprise at the time as they were long established routes acquired with the take over from BA Connect. I'm sure the bean counters know what they're doing (one would hope at least).