You can not put 2 equal items in the hotbar

Steps to Reproduce

1. Take two equal items, for example: (two iron swords).
2. Then try to put both in hotbar.
3. As you can see only the first one goes to your hotbar. And whenever you select the second item will put the first

IMPORTANT: Two equal items can only be placed in the hotbar if one of them is enchanted or the amount of one of them is different