/clear command does not clear the player's inventory

I cannot seem to replicate this bug anymore...

 

The items were cleared after I reloaded the world.

 

How to replicate:

Run the /clear command on a player.

Expected behavior:

All items in the player's inventory gets removed/cleared.

Actual behavior:

No items are cleared from the player's inventory, and the error shows: "No items were found on player (Player username)"