Since 0.58 inventory glitches have gotten even worse. If you drop backpacks or guns they "quasi-dupe" for other players to access your inventory and ammunition slot in the gun while you're miles away.
Quantities of ammo do not change when you add rounds from other piles. I've had single items that took up double bag space and when I dropped one on the ground, the double would also disappear from my bag. If I picked it up again, two would appear in my bag.
Food you've eaten can become "stuck" in your bag (can only "Receive...", had to drop backpack and ask a friend to drag stuck can of sardines out of the bag)
I've had a friend pick up the oil barrel that was in my hand because for him it was meters away from me (where I'd last dropped it) and it disappeared out my hands and into his.
The list goes on and on and on.
The last time inventory was this unstable was about a year ago.