The world is not fully synchronized or is damaged. Try playing in this world with a console in which it is in good condition and then try the file migration again.
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[media]
[Mod] OcelotOnesie
Thank you for your report!
We're actually already tracking this issue at MCPE-40552, so I will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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