I can't ban a griefer... says SERVER: Error while trying to kickban ip: The person trying to ban is not logged in.
Never happened to me that thing before
He came and griefed my drawing I spent hours in :/
That's cause you weren't logged in. Refreshing the page can help in those cases.
*Edit*
This combined with the bot stopping might mean the player server crashed or something. Anyway next time this happens logout and in again or refresh the page.