I believe this is the place to bug this since the Realms section only uses Java version numbers. I am the server owner of my server and have been trying to replace my current realm world as so we can actually enjoy the new world generation of the village and pillage update. When going to replace world (my world I am looking to upload is only about 22.8 MB) I select my world to upload. It says "Export in Progress" with a popup that says "Level export started..." and the green bar quickly fills up from 0.0 MB to 0.0 MB. The popup says "Level Export finished succesfully". It then immediately goes to the next screen which just says "Failed". No further info. This happens on both my android and Xbox One platforms. As a sidenote, it also does not allow me to replace my world with backups that have been saved.