I killed the dragon. The end gateway took me back to the island spawn instead of out to an island. I then loaded up a new test world and again the gateways didn't work. On top of that I respawned the dragon and instead of putting the crystals back on the towers parts of them blew up and there were some of the explosions in thin air like the crystals were trying to spawn.  The dragon was swiftly defeated with no shields and again the end gateway did not work.