Major Trying to put a breaching charge into a full container arms it

[Zafhset]

Exactly as it says on the tin. If your backpack is full and you try to put a breaching charge into it, the charge arms on the tile you're standing on. Obviously causes issues if you're the HoS in the Manta armoury or a nukeop on the shuttle.

Having the backpack be full is the only way to use an item on the backpack instead of putting an item into it. To paint a backpack with a paint can you have to fill it up first. 

It's simple enough to just keep an eye on how full your bag is before dumping stuff into it - would not recommend changing this behavior as it would remove one of the ways you can interact with the bag.