[MC-69083] Minecraft PE High in the sky on startup

In Minecraft PE I start a world and start mining huge mine shafts at bedrock level then I turn it off for a few hours. when I load the world I am instantly over 21 blocks high in the sky and I fall to my doom loosing all my items.
It happened about 4 times already and it os getting annoying. I am using no tipe of mods , cheats , hacks ,exc . I think is has something to do with the limit world size experimental setting for now I have it off. Don`t believe me look at the video still don't believe me Ill say this in the video "321".wathch all of the un edited videos at youtube because they where too large for this report.
http://youtu.be/rdPaGQWHDUY