Put the summary of the bug you're having here

What I expected to happen was...: I was playing normal survival and I wanted to switch from axe to sword. I was about to press (1) I press (q) at the same time I was pressing (1) and I dropped my sword and my axe. But my sword only showed and not the axe because there was nothing in my inventory slot that my axe was in and when I press (q) on the slot that my axe was in it dropped. I experiment on this and when you place a item on the same slot that my axe was in it deleted. if you do this with items that can stack it can dupe it by 1 item. I was on 1.16.5 at this time (i can't run 1.19) and the dupe only works one time for stacked items.
Describe what you thought should happen here-

ill drop my sword but not my axe

Describe what happened here

What actually happened was...: ill drop my sword and my axe if i press q on the slot the axe was in it will bring it back, I tried with stacked items, and it duped it by one item 

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ... have 2 items(no stacked unless want to do dupe glitch)
3. ... press any number button next to the second item when doing that press (q)