What LCD and macguba said is true, but when I had the same problem, I solved it the hard way...
First off, I named every single soldier. Then, I made a script like this that was activated shortly after my eject script:
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unassignVehicle off1
unassignVehicle off2
unassignVehicle off3
unassignVehicle mike1
unassignVehicle mike2
unassignVehicle mike3
unassignVehicle mike4
unassignVehicle mike5
unassignVehicle mike6
unassignVehicle mike7
unassignVehicle adam1
unassignVehicle adam2
unassignVehicle adam3
unassignVehicle adam4
unassignVehicle adam5
unassignVehicle adam6
unassignVehicle adam7
unassignVehicle david1
unassignVehicle david2
unassignVehicle david3
unassignVehicle david4
unassignVehicle david5
unassignVehicle david6
unassignVehicle david7
[off1, off2, off3, mike1, mike2, mike3, mike4, mike5, mike6, mike7, adam1, adam2, adam3, adam4, adam5, adam6, adam7, david1, david2, david3, david4, david5, david6, david7] allowGetIn false
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