Bugs in Minecraft PE are rare. Just one year ago you could find them at almost every turn. But Mojang are working hard on them. We have prepared for you fresh-found a bug, but rather a seed, where there was the generation of the mine on the surface.
This seed generates a mine directly on the surface and not underground as usual. Seed is for Minecraft PE 0.15+
When generating the player sees the following:
I think You have already noticed rails that are usually found in the mine. This is the error generated. Here are the screenshots:
On the last screenshot shows that the mine has continued, where You will find many ores and tunnels.