I am unable to upload/replace worlds on the Minecraft Realms service. I play the game mostly on the Nintendo Switch and Xbox One, though I do have the Android version as well. I have attempted multiple times over the last several months, various things recommended by the Mojang support staff, and various things on my own, and I am still unable to upload any world to the service, regardless of the platform, which means that I am unable to transfer my worlds between platforms as described in the Mojang help article. The service will create new worlds just fine, it just won't upload/replace them.

When I attempt to replace a world, regardless of platform, the game will act like it starts to upload it, but there is 0% upload and 0MB that takes place throughout the "fake upload". The game will eventually say the upload is complete as if it has successfully uploaded to the service, going so far as to usually display said "upload successful" text, though after doing so it will only displaying the moving status bar with the "Cancel" option. Larger worlds (around 500MB or so) will usually cause the system to crash.