While speedrunning, me and a couple friends were fighting the Ender Dragon. Both of my friends died, but when they tried to comeback to the fight, the Dragon went and flew down to the spawn platform and bunted/acid spewed to death. This would occur every time they entered the End. The Dragon also would fly away from the Platform but then instantly come back once someone spawned.

This is very critical and should be fixed ASAP as this can ruin multiplayer games

Here's a link to a video during that attempt: https://www.youtube.com/watch?v=WXxVNOSB5hI&feature=youtu.be