Ender dragon spawning and regenerating are very broken

When you enter in a end portal for the first time the ender dragon doesn't appear and same with the end portal in 0 0 in the end island. And if you regenerate it in creative mode (building by yourself the end portal with bedrock) the Ender Dragon appears but the end crystals towers  not regenerate correctly.

You can see this at: https://youtu.be/HyApkEUuJVs