F.F.B. Plug-in

I'm playing the F.F.B. plug-in, and when I complete a mission for either the Rebels, of the Confeds about searching the Sepens Nebula for planets that are under control by the Red Aliens, the mission repeats itself. I accept the mission for the Confeds on Mars, and Palshife for the Rebels. Why does the same mission repeat?

"Let it go. If it comes back, it was meant to be. If it doesn't, HUNT IT DOWN, AND KILL IT!!!"