It could be many things:
- Caused by the way Flarum counts posts
- Caused by a missing refresh of the posts count
- Caused by an extension altering how posts are counted
It's hard to say which one it is without knowing the full context. Is the post deleted, is it inside a deleted discussion, is it in a discussion any guest could see or not, is it flagged or awaiting approval?
You could try creating more posts to see if the counter updates and possibly fixes itself or not. If despite updating it's still not counting some posts, we need to find what the common aspects between those posts are.
There are some known issues with the counters tracked at flarum/core1006 and flarum/core2240 and possibly others, but it's difficult so say if your situation is one of those.
An extension could cause this on purpose by modifying the counters, or if an extension caused an error during post save or update it's possible it prevented Flarum from updating the counter.
