Shouldn't even be possible in the code for posts to get posted to the wrong thread. Can you give examples of this happening? Are you certain that you're replying to the correct thread?
When you say "disappearing altogether", do you mean that the posts appear in the thread, but then they disappear at a later date? Or do posts appear and then you immediately refresh and they are gone?
When you say "disappearing altogether", do you mean that the posts appear in the thread, but then they disappear at a later date? Or do posts appear and then you immediately refresh and they are gone?