If a map is placed inside of an item frame and then you quit to title and then go back into your world, then the map will be invisible and it will only show an enlarged item frame.
MCPE-12652
Maps turn Invisible Inside Item Frames
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
Tablet - Android - Samsung Galaxy Tab 3
Android 4.4.2
0.14.0 Beta 1
Retrieved
Thank you for your report! This issue was, however, reported at an earlier time as MCPE-12643. Feel free to add any information you find relevant in the comment section there.
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