If you have two of the same items in your inventory: One locked, one unlocked - when using or quickstocking, the action always goes to the unlocked one, no matter which you click.

IE When quickstocking, the locked item will be quickstocked, and the unlocked one will remain in your inventory (and it is unlocked) When using an item, the locked one will remain, and the unlocked one will be used up.

Have had tested this several times.

Just to confirm this is still an ongoing issue. Good thing I found this! Was about to create another thread.