When blocks of value are placed down like a block of diamond or iron, when the world is quit and then logged back into, the blocks disappear. This also occurs in creative as well as survival but it first happened to me in survival. It don' affect per-0.6.0 worlds.
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duplicates
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Duplicate of MCPE-1217, please use the search function to see if your bug has already been submitted. Currently over 50% of tickets are being closed as duplicate.