Supply box ammo bug

I constantly have issues with the supply boxes not consistently giving me ammo.

Example - I have 0 grenades, I'm standing on a box and my grenade is filling up it's progress bar towards 1... it suddenly stops, I haven't moved away from the box, the box is still there... If I throw a new box the progress continues until it randomly stops.

This happens to me constantly in every match with every type of gadget etc... it's very frustrating.