I can't use experimental gameplay or copy my world...

I really want to use structure blocks, but I need to have experimental gameplay on. I go into my settings, turn on experimental gameplay and it gives me heads up that it might break my world. I press continue anyways and I expect it to make a copy of my world. Instead a notification pops up on my screen saying that it failed to copy world. It's not only my experimental gameplay, but also the copy world button and education edition button. I believe that it's because I created the world a long time ago because I did the same thing but instead I generated a new world and it worked. I would appreciate it A LOT if you could fix this problem really soon for me to add old creations into my city world.