Chunks of The World Has Been Deleted

After the latest update, it said they were making the worlds smaller by a certain amount of blocks, which in itself is a bit bizarre, as an Infinite world should be infinite? When I went on my world, random sides of the world have been deleted all the way down to bedrock, in a messy way. The world also has glitched out random parts, that even when walked on, or placing a block, is still glitched out. The second and third photo is of the deleted chunks, the first is of the glitched out parts.

EDIT 17/04/18
I have attached a new screenshot, of a building that is half glitched out. The glitching is getting worse!!

EDIT 30/4/18
Its getting a lot better! Whatever you're doing is working, its almost fixed completely! There's just a little band that still needs closing up, but after that, the world goes on infinite! So Thank You for working on it It just needs a tiny bit more work