Enderman not disappearing and freeze when switching to peaceful.

In the End the Enderman surrounding the area in the main island wont disappear and become frozen when I switched to peaceful. I cant damage them and can easily move through them, they also don't make sounds anymore but their particle effects are still active. Switching back to easy normal or hard doesn't change anything, the Enderman still cant be damaged and don't move but new Enderman do spawn and do behave normally. It happened after I defeated the Enderdragon in creative.