As usual, a bug that has existed for a long time.
In the first place, it is a matter of not moving zones (including transports) while casting and just holding back for a few seconds, but I write this just in case.
If player does various transports (Home, Guild Castle, transports to various locations, automatic forced movement during quests, etc. Whether voluntary or mandatory) while using (=casting) an item with a casting time (such as "Potion: Scarlet Love"), after the move is completed, the message "Cannot be used" will appear and the item that was in the process of being cast the item can no longer be used.
This can be fixed by returning to character select once or re-login.
(Before, the icon of the target item in some cases would be grayed out, I think.)
That's all.
