Those errors usually mean websockets are not proxied correctly, make sure your nginx setup is correct. If you are using cloudflare you need to disable acceleration. They don't support websockets on smaller plans.
Teaser Settings set to "first" but shows "No replies" untill someone comments
When you create a thread, it is supposed to show the actual text in the thread on the teaser when Teaser Post is set to "First"
It also does show the text in the teaser, but only when someone comments (It does not show the actual comment text)