Same problem here. Although not only related to M4 but anything you hold in your hands. Not good when you are low on ammo already and then waste it to that glitch.

The glitch is not the ammo box but the possibility to unload a coupled mag into a single stack of 60 rounds, as also stated in Issue #6598

I think it would be a major issue on development in the engine. It's not a "bug" but a quite development expensive feature that was missing from Arma III from the beginning.
I'd say, save the developer capacity for less expensive features of the gameplay.