I've paid a small fortune in Minecoins to purchase worlds for my son and on a regular basis the worlds that are created refuse to load and display the message in the title. He's 5 and gets pretty distressed because the worlds won't work and I can't figure out why or how to fix it.

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Worlds that have not been created from a template work fine. Those are not the worlds he wants to play.

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Deleting the app and completely uninstalling everything is the only thing that gets the paid worlds working again. That, however, is not a solution to the problem, and causes more distress since things he's create are obviously deleted.

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I found one other issue on your Jira and the issue was closed prematurely without a solution, which is also another point of frustration.

Excuse the frustration above. A possible solution, in order to help the development or QA team recreate this issue,is to load a paid world. It won't load. If I load another paid world, exit, and then retry the original world, it works.