So I'm on my second non-tutorial mission and several of my soldiers are shown on the launch menu as "On Mission". I've tried repeatedly to replace them with available and healthy soldiers on my dropship but whever I try to launch a mission, my craft refuses to update my available soldiers and I have no idea why a third of my squad are just rendered unavailable. What does "On mission" even mean, in a context where I'm not launching any other missions and all my soldiers are on base?

I'm going to refund unless I get an explanation as this seems like a pretty serious bug.