I can't remove any of my Duty Officers from active duty. It doesn't seem to matter whether it is space or ground. If my roster is full (I only have 4 in space; I'm trying to switch out ground, which is full), and I try to add a duty officer to the full active roster, it simply removes the first-listed duty officer and puts in the one I just tried to add. When I try re-adding the one it took away, the new officer I just added is replaced, so I can't even do a rotation scheme as a workaround.
This is on a KDF toon, if that matters any.
It looks like having a full roster is what messes this up. I dismissed an unnecessary guy and removing/adding to active roster worked just fine with 99/100 slots filled.