[_ck_]

That query IS working properly on my test copy.

I purposely changed the topic_posts on a topic from 46 to 99.

Then ran this

INSERT INTO bb_topics (topic_id, topic_posts)

(SELECT topic_id, COUNT(post_status) as topic_posts

FROM bb_posts

WHERE post_status = '0' GROUP BY topic_id)

ON DUPLICATE KEY UPDATE topic_posts = VALUES(topic_posts);

and it reverted it back to 46

So try changing the 80 to 81

then try the above query and see if it changes it back to 80 or not?