Equipping two items with an attribute modifier of the same ID and affected attribute and unequipping one of them removes the modifier even when the other item is still equipped.

How to reproduce:

1. Execute the following command: 

   /give @s carved_pumpkin[attribute_modifiers={modifiers:[{type:"movement_speed",id:"speedy",operation:"add_value",amount:1d,slot:"any"}]}] 2

2. Make sure the pumpkins are not selected in your hotbar, then put one of the pumpkins on your head.
   → You will have the speed effect, as intended.
3. Now scroll past the other pumpkin in your hotbar.
   → As soon as you unselect the pumpkin in the hotbar, the speed modifier will be removed, even though the pumpkin is still on your head.

Expected result:

An attribute modifier would still be present even after unequipping one item with the modifier but keeping another.

Observed result:

An attribute modifier is removed after unequipping one item with the modifier, even if another item with the modifier is still equipped.