Description:
In the following situation:

• A "/item" command (that modifies slot X) is contained within a reward function of an "inventory_changed" criteria advancement.
• Slot X is changed on a player that has their inventory open and is in creative mode, triggering said advancement.

The original item change on slot X that triggered the advancement overrides the modification made by the "/item" command (even though, logically, the "/item" command happens after, and should affect the final item).

Furthermore, if the reward function of said advancement contains a command to revoke the same advancement and the same situation occurs:
For as long as the player stays in creative and keeps their inventory open: The item generated by the "/item" command and the item from the inventory original change will "fight" repeatedly in slot X. Once the player exits creative mode or their inventory, the item generated by the "/item" command will finally occupy slot X.

To Reproduce:

1. Create a world with the attached datapack.
2. Attempt to put any item from the creative inventory in the first hotbar slot.
3. Observe that the slot rapidly switches between a slimeball and the item placed in the slot until you exit your inventory.

The attached datapack contains the advancement 'example:inv_change' which triggers on inventory change, and has the following reward function:

execute unless items entity @s hotbar.0 slime_ball run item replace entity @s hotbar.0 with slime_ball[item_name='{"text":"example"}']
advancement revoke @s only example:inv_change

A video is attached demonstrating the bug behavior.

Note:
If the "/item" command is replaced with "/clear", the item in the first hotbar slot is simply cleared as what is logically expected.