The Enderdragon doesn't attack the player and instead flies in a small loop. Doesn't stop looping unless I relog (this is on a server). Despite relogging it will move for about a second and then start looping again.

When all of the end crystals are destroyed the enderdragon begins to fly in a small circle indefinitely. Unless I leave and join the server in which case it will move for about a second and then get back to flying in a loop.