My friend and I are playing on a private server. When we went to the end, the pillars and end crystals were there, but the dragon and its bedrock roost thing weren't. I went into creative and replicated the bedrock thing and started placing end crystals to try and respawn the dragon. After I placed a crystal or two, the actual bedrock roost appeared, so I broke the one I was making and placed the four end crystals around that bedrock roost. After the dragon spawned and we killed it, the end gateway spawned. Upon trying to throw a pearl in, we were instead teleported to the obsidian platform you spawn in on when you enter the end. I've tried resetting the end via deleting the DIM1 folder and deleting the information under DragonFight in the level.dat with an nbt editor but I got the same results. The effect is replicated when recreating the world by using the same seed (6411276314725874163). Something interesting to note is that in the replicated world, even though the bedrock roost wasn't there when I entered, it and the dragon appeared when I walked over the location where it should be. However the gateway still lead me to the end spawn instead of one of the end islands.