Bug description: After the second or third player death in The End during the Ender Dragon fight, the return portal in the center of The End activates before the dragon is dead, allowing the dragon to travel to the Overworld and destroy everything around 0,0 (or the default world spawn point).

Recreating the bug: Activate The End Portal in the stronghold, set your spawn point using a bed, and enter The End. After your second or third death while fighting the Ender Dragon, the return portal in the center will spontaneously activate before the dragon is dead, allowing the dragon to use the portal and travel to the Overworld. The dragon will be sent to the default spawn location for the world in the Overworld, where players spawn when they first enter the world.

Extra information: This can happen in either survival or creative mode. This was all done while playing alone, but cross play was activated. This bug repeats itself if another dragon is summoned in the end using the crystals. After about three player deaths, the return portal opens before the dragon is dead, allowing the dragon access to the Overworld. My world which was affected was generated pre-aquatic update phase two, but The End wasn't generated until after the aquatic update P2. I generated a new world in the aquatic update P2 in creative mode to see if I could replicate the problem, and I could. If you fight the dragon all in one go, without dying and reentering The End portal from the Stronghold, the fight works as intended, and the center portal activates after the dragon's death, along with the portal to the outer islands in The End.

Ask if you need more info. Thank you!