凡ミス（よくこれで 1 回め通ったな……）

update_db.py

@@ -663,7 +663,7 @@ class VideoTagDao:
                       untagged_at = %%s
                     WHERE
                       video_id = %%s
-                      AND tag_ids IN (%s)""" % ', '.join (['%s'] * len (tag_ids)), (now, video_id, *tag_ids)))
+                      AND tag_id IN (%s)""" % ', '.join (['%s'] * len (tag_ids)), (now, video_id, *tag_ids)))
 
     def _create_dto_from_row (
             self,