Mother Base staff with "?" icon locked to them.

[Defensive Bias]

I have no idea what it means. Some of my staff are locked into their positions and have a "?" icon next to their picture. Barely finding anything that confirms what exactly it means.
http://steamcommunity.com/sharedfiles/filedetails/?id=851977448

[F430]

Check further down your intel team tab and see if Ziang Tan also has a question mark.
If yes, then that's because they've both been captured and you have to complete an Unlucky Dog side op to get them back.
Otherwise, depending on where you are in the game, there is a story mission associated with rescuing that staff member.

[Coyote Knight]

Depending on how far you are into the game, it could also mean that guy was captured by someone who invaded your FOB.

[F430]

Actually, no.
If that happened, they would be listed in former staff tab with red text saying "killed or extracted by rival".

[Coyote Knight]

Originally posted by F430:

Actually, no.
If that happened, they would be listed in former staff tab with red text saying "killed or extracted by rival".

Can you replay the unlucky dogs side ops after getting 100% game completition though?

Because if you can then that would explain why I can't interact with them while on the staff tab.

[Defensive Bias]

Yeah it's not the FOB cause I don't have any reports of getting invaded.

[F430]

Yeah, Unlucky Dog ops are non-repeating, just like the child rescue ones, so they won't respawn.
And if by interact you mean move between units or dismiss, then it would only be Ziang Tan and key story characters.