Slitherine

Battle of Lashkar Gar.
After a while, every time I send a unit to the maintenance area I lose the unit. I thought it could be because there was an attack on it but no, that's not it.
I've lost that way 2 chinooks, two husky and a Buffalo. What gives?

I use the top-center "unit counter" button (the one with the swooping arrow above it -- not the next and previous) button to cycle my units. This seems to reset units that disappear into the maintenance area. I usually do it at the end of a turn to review units I haven't moved yet.