The server processing the forum seems to have a short timeout enabled. If you spend more than about 20 minutes posting a reply, its likely that when you come to post the reply, the message will not post and you will get a red error message.
An understanding user can reinstate the session without loss of the reply message, by copying it to clipboard, refreshing the screen, starting a new reply and pasting the reply back in. The repost will then succeed. But this is awkward for the average user and should not be necessary.
It seems we should probably have either
- a background task that accesses the server every 5 minutes while composing, to ensure the server remains connected throughout, or
- perhaps simpler, the Post Reply button could pre-check if the browser is still connected to the server before posting the reply and reconnect it if it is not.