When you break something below Y:0 and exit the world then rejoin, the previously broken blocks place themselves back. (This is another post because I don't know how to edit an old one)
Link to new video:
https://www.xbox.com/play/media/NNY5PL5D
MCPE-157701
World below Y:0 doesn't save
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Duplicate of previous report (MCPE-155565).
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