Ender dragon crashes when building above the exit portal

Building above the exit endportal will lure the dragon there to do his breath attack but as soon as u hit him once it will crash the game staying in a crashloop not beeing able to start the world again...further on endermen will attack the dragon and kill him without a player shooting 1 arrow or doing 1 swing can just sit afk in a hole,eat food and after like 15 minutes the dragon is dead