This issue have been fixed. After updating my game there was one ender dragon, as things should be. Althought, now the dragon would fly to it´s original position and stay there for a little while, leaving waaaaay to many free hits.

I'll miss this bug because it was kinda hillarious. But thank you for solving this Mojang!

Short version: So, I finally got to the end which I am pretty sure I will meet ONE dragon, but no no no, there are FOUR OF THEM!** Now I'm stuck here, unable to "finish the game!" Also, the game crashes. Note that this is a pure and fresh no cheating vanilla survival world!

Full story: Finally, time for the endgame. I enter the End to defeat the Enderdragon once and for all. The boss tab appears and as I walk closer to the pillars, another... boss tab? And another and another?? I try to hit the crystals but four dragons vs one player make it frustrating and right down impossible no matter how good the gear is! I can´t cheat without losing my achievements, besides you shouldn't have to cheat to be able to beat the game! Either I die or the game crashes before I know it! How should I beat the game now?