Ender dragon won't die

After killing the Ender Dragon, the death animation plays, and the light explosion happens, but the dragon's health bar remains visible, empty, and the portal to the Overworld does not appear. If you close and reopen the world, the death animation starts again, but this time the dragon's health bar is full. I can't make any progress. The image is from after reopening the the world, also the fps drops below 10 and the game eventually closes