When picking up ammo from a bot ammo fixer with a nearly full weapon and partially spent magazine, it will load the magazine with explosive ammo using reserve ammo.
For instance, if I have 10 in my (14 capacity) Combat shotgun with 72 ammo, picking up a bot's ammo bag will give 14 magazine and 68 ammo. I will need to pick up the bag again to refill the full 72.
I noticed this mostly occurs at full and completely empty ammo. With an empty gun, sometimes the magazine won't even fill and I can end up with a partial magazine + reserve ammo to reload.
This is a small bug and not a big deal, but good to note.