I put this under bugzilla, but I'm not sure if it's a bug. Using either Fred2_Open 3.5.3 or Fred2_Open 3.5.5, I see a bug under the Mission Specs Editor.
If you select "no briefing" or "no debriefing" under Mission Specs of Fred_Open, they will not unselect if you exit the editor, return to mission specs, and click on them again. This happens under Fred2_Open 3.5.3 and 3.5.5. You can unselect them and hit "OK" but if you go back into the mission specs menu they will be selected again. If you unselected them, save, and try the mission (in case it was opening up mission specs editor that selects them), the mission will have no briefing or debriefing.
This is a little fustrating as I clicked on "no briefing" and "no debriefing" when I started fredding this mission so I can get quickly into the mission to test it. Now that I want to see the briefing, it doesn't let me unclick it

Can anyone see if this is something that happens to them too?