After an AT/AA unit respawns it has one AT missile less than it had when it started the mission (the missing AT/AA missile is the one loaded into the launcher).

A possible cause of this is that when the soldier gets his gear after respawn the rearming script first gives the soldier his backpack (filled to max capacity with 2 missiles) then it tries to add the 3rd missile (the one that is normally loaded into the launcher) with the command "soldier addMagazine 'titan_at'". And the addMagazine doesn't add the 3rd missile because it needs to have some space in soldier's backpack (the addmagazine command first adds the item to player uniform/vest/backpack space then this item is automatically loaded into the launcher that is added later with the addWeapon command).

So this case maybe related (consequence of) to the case http://feedback.arma3.com/view.php?id=14255 about addMagazine command bug.