I have had strange things happen before to me while playing this game. I had a world when updated to 1.16 when I killed the dragon again it dropped an egg. I've seen a lot of crazier things. One day while playing on a legit survival world I was trying to go to the end islands by using a flying machine. I failed several times but one time I did get out very far. I gave up and thought I would try at a later date. However when I went to my home base which is right next to spawn something strange happened. I don't remember exactly but I was in my starter house minding my own business when I started hearing flapping noises. And then a dragon sound effect played. I went outside and felt a lag spike. I proceeded in the perceived direction of the cause and there in the ocean next to my spawn was an ender dragon. I know it sounds fake but I'm serious. It had a boss health bar and everything. It demolished my ocean and cause a lot of lag. Eventually, it disappeared but now in my Nether, there was an Ender Dragon. Boss health bar as well. I went to the end to see if there was a dragon there and there wasn't. Eventually, through experimenting on a copy I realized that I couldn't respawn Ender Dragon. So I killed the dragon in this creative copy that resided in the Nether. After that in this copy world, I tried to respawn the dragon in the End. It worked! I then did this in the actual survival world and now the only remains were giant holes in both a regular ocean and holes in a lava ocean in the Nether. There is also a floating dragon fireball in the overworld. If you have any suggestions on how to get screenshots from my switch to here I will try to do so. 

Seed: -23334877

First update world was played on: First full release of 1.17 for Bedrock on Nintendo Switch