Problem: Picking up weapons deletes stackable items.
I'm surprised this hasn't been reported yet because I believe it is effecting all items in stacks. Since the second to last patch that increased the number of slots many weapons take up, there has been a rather severe bug. Picking up weapons off the ground, deletes a number of stacked ammo or weapons from your person. It is hard to reproduce it under the same exact circumstances during a battle, but it happens almost every time. I will cite examples to try and help.
For instance I will usually enter play carrying two stacks of throwing spears. They take up two slots each and give me 4 per stack, so I have 8 in total. I will for instance throw maybe 4-5 of these, having 3-4 left. I should have two slots free. Sadly picking anything up deletes either all but one throwing spear, or deletes them all leaving me just with what I've picked up. I am not picking up multiple items, or three slot items. This also happens when picking up other throwing weapons. Usually if I pick up a single war dart, it will remove ALL of my remaining throwing spears leaving me only with the single dart while tincans rush at me. Not the best situation. The deleted weapons do not appear on the ground, and there is no way to get them back until a new round starts (provided I die and don't start holding what I picked up.)
I have also been able to reproduce this problem with a crossbow and bolts. Holding a 1 slot crossbow and 1 sack of bolts, I have found that picking up a weapon from the ground will destroy the bolts leaving me with just a crossbow, or sometimes dropping the crossbow and leaving no trace of the bolts. I have not tried it with arrow quivers. Sometimes having exactly a full stack when picking up an item leaves that stack alone, but I can't reliably say for sure.
I can't express how crippling this, especially coinciding with throwing taking such severe overall hits. I need all the ammo I can get since I cant retrieve shots from bodies. When this happens, the round is game over for me, especially when I pick up a throwing weapon and it deletes the rest leaving me with just that one shot and my fists.