This bug seems to appear after logging out of the Game do to an inventory Bug. Like items can't be moved around the inventory, can't be dropt or Picked-up ,or weapons can't be reloaded. While having a packed, but not full inventory.
After logging in again items often disappear from the inventory at random. It can be a Cann of food, a weapon, ammunition or bandages.
It doesn't seem to have a pattern.