So, basically this bug cointains one more bug in it, so lets get started:
1.(mobgriefing must be off) Going in the end and running the command : execute @e[type=ender_dragon] ~ ~ ~ setblock ~ ~ ~ portal, a couple of times until the dragon disappears and the home portal opens up
2.Back at spawn you see the dragon but with NoAI, and if you unload the chunks , it dissapears.