I was playing on server and experienced an inventory bug, when two items were on same slot in my inventory. I was also unable to load FNX magazine at first.

Time in video:
3:05 - unable to take magazine to inventory with F button while I have something else in hands
3:18 - dragging empty FNX magazine to hands and magazine appered on gun in inventory in jeans (two items on same slot)
3:23 - dragging magazine back from hands to inventory and two items on same slot bug is fixed
3:34 - I take another magazine partially full to hands and it works normal, starting to filling mag
3:47 - taking that empty mag from inventory to hands and it start to appearing on gun again, unable to fill magazine with rounds trying to fill it 3 times with no success
3:58 - I put my magazine back in inventory with double click and it appeared on the gun
4:05 - dragging magazine from gun to hands - it not longer appears on gun
and I am able to fill it with rounds
4:16 - double clicking on magazine and it appeared on gun in inventory
4:19 - dragging magazine from gun in another slot in inventory, taking gun in hands and magazine again appeared on the gun in inventory
6:00 - dragging gun from inventory in the hands, dragging magazine from one slot in backpack to another slot in backpack and that magazine appeared in jeans
6:07 - dragging gun from hands to backpack - it works normal

Check additional info and video