I ran into this today and I think it’s caused by deleted topics.
Steps to reproduce:
- Create a new topic and add to it a new or existing tag;
- Navigate to the
/tagspage and memorize the count next to the tag you added to the new topic; - Delete the new topic;
- Go back to the
/tagspage and you’ll see the tag count isn’t updated.
I can reproduce this constantly on my local install.