Remove from you uniform any items (grenade, magazine, etc..), and after change you uniform to uniform friendly dead unit (using right mouse click).
Then, I no have any items for use, though the dead has items inside uniform.
No items in uniform not loaded for my use.
And this problem also, if I have more throw in my uniform and then change uniform.
Then some show me that I have 0x pieces of items.
There is no problem with change vest, only uniform. Tested in version 1.80.
It is badly explained to by my English, it needs to be tested.