Enderdragon not spawning

Hey Mojang-Team,

After successfully entering the end, trough a naturely generated endportal,

I found myself on the main end-island(obsidian platform), with all the end-crystals active but neither the enderdragon, including it's health bar, nor the home-portal spawned.

I reset the "DragonKilled" and the "PreviouslyKilled" tag to 0 on a copy of the world, but just fixed the "Health-bar porblem".

I really want to kill the enderdragon to start my basebuilding in the end,

still hoping for an easy fix in the next snapshot.

Yours KunzGrunz

P.S. The world-file is too large for uploading it, so I added this link to my dropbox:

https://www.dropbox.com/s/jjdxvo55y2sl8vo/Taryen_old.zip?dl=1