Open Library
Select multiple books that have no tags yet
Click "add tag" and type "A" to add a simple tag to all of them at once
Click the edit pencile next to this new tag you've just added, and change the text to "B"
Result: it adds a new tag "B" to all of the selected items but does not remove the previous one "A"
Expect it to edit the "A" tag and change it to "B" so you're left with just one tag still