That's my biggest issue. I'd spawn him under ground and have a huge cavern afterward. Now I can stand in 2x2 hole in stone and he wont even touch me. I end up with a hallowed out area that could have been mined in 2 minutes.
When I enter the End, the ender dragon freezes in place and flaps his wings. His health bar disappears and the exit portal opens. I respawned him using the end crystals and the same thing happens. All this on survival. I went on creative on several other worlds and had the same outcome. I kind of feel sorry for him. Relegated to a lifeless abyss of stationary flying. Then I realized I can't get the 50 XP that comes with defeating him.
I guess I'm not getting an explanation for this