If you play any kind of gesture, while a unit is reloading, the reloading functionality will completely break for that unit permanently for all it's weapon slots.
The magazines will just disappear from the inventory when you press your reload key and nothing else will happen.
Fixable by dropping all weapons and picking them back up again, however that isn't a permanent solution.
This seems to have been fixed in todays build.
The reloading no longer gets broken, but you still lose a magazine (the one that was supposed to be the new weapon mag) if you play a gesture during a reload.
I do not know if this is the intended behavior.
Why I think it's probably not intended.
This destroys the item completely from the game world, it no longer exists, it's not on the ground to be picked up again, it's basically gone forever.
The magazine was taken out of the player inventory which is not players inventory and because the reload was aborted, there was never the moment when the magazines would exchange places or returned to the inventory.
As if something like this is happening:
Begin reload -> Remove magazine from inventory -> Wait until magazineReloadTime is complete -> Put magazine in weapon -> If the magazine that was taken out of the weapon still has ammo, put it back in the inventory
The problem there of course being that if the reload was aborted, the fresh magazine would be lost from the game world.