When I delete units from staging areas (on desktop or mobile) they don't always go home, a few of them decide to stay there even if the staging area expires (as in it runs out of time and disappears) they just stay there. You can make them start going home by sending them to a mission and then cancelling it.
I have over 80 vehicles so that could be causing issues but it's still really annoying.
I messaged the devs about this a whole back but have yet to receive a response and seeing as we now have a forum I thought I should post it here.