This happened all of a sudden while i was working on a map and importing structures to it. One of the structures had a nether portal and when i went through the portal and back, this happened.

Steps to reproduce.
1.Have luck.
2.Place a nether portal.
3.Go through it and back.
4.Hope it breaks the terrain.

This is very bad as it could mean a new way of breaking bedrock.

Other Notes
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"2017-06-22_15.16.14.png" is the nether portal with the coordinates.
"2017-06-22_15.16.43.png" is the nether portal destination with the coordinates.
"2017-06-22_15.16.55.png" is what the terrain is supposed to be if it wasn't for the portal.
"crash-2017-06-22_15.21.41-client.txt" is the data from when i debug crashed my world.