Can you write down more details?

Where was a clip located?
Were your hands empty at that time?
Was there any storage space in your Inventory or it was full at that time?
Have you got 2 weapons on you or only one or none at all?

If you write down a test scenario then I will try to reproduce the issue.

ATM there is so little info that I can't even think of a possible scenario I should follow.

the magazine was in the backpack.
i had a MP-133 shotgun in hands.
as i recall, i had no storageroom left.
as i said the shotgun in the hands, a CR527 carbine on the back, a magnum, and the 1911.
i just threw out the makarov to pick up the 1911 and change suppressor, pistol flashlight that i had on the makarov. after that i wanted to put in the magazine, but it didn't work, i guess it was a connection problem. (i cant recall whether the 1911 was in the inventory or the vicinity)
but finally i tried to empty the magazine to check if it is still in the inventory or already in the 1911.
it kind of worked. after that the ammunition and the magazine were in the same slot.

Thank you for writing down more details. I will test that scenario and write down the outcome as we all want that no item would disappear.

Ah f*** forgot to mention, i'm using the new ui. Sorry... :/

But i got the feeling anyways that since im getting comfortable with the new ui, a lot more stuff gets lost during any inventory and vicinity actions, or even eating/drinking actions while holding something in the hands.

Thank you.

same thing with the cr75.
and i think i know the problem. it occurs when you want to attach the magazine to the pistol while it is still on the ground and not in your inventory or your hands.
when you try to do this the magazine stays in the slot and is not in the pistol, but from then on its only purpose is to empty it. the ammo then is in the same slot as the magazine.