I went to add the artist for post #3380377 but I always check if the Pixiv ID is there, and noticed the artist already existed as artist #181534 so I only had to add the artist to the post. But the artist name Tub is also the general tab 'tub'; the post already had such tag. Now searching for the tag shows all the tub posts plus the new one. So now the artist should be renamed, and I think only the post I mentioned needs to be retagged (removing tub and adding the new artist name) as these changes were made very recently. No idea of how to proceed, so if someone who knows can take a look, thanks.