It is not the first time when I generated a new world, and it is generated square lakes, and big square cutted hills. It is also cut off water flows, and water don't flowing. For example. in this seed: "-4259845526421387129" (world type default)
It has square biomes, square lakes, and square hills. You are able to see them in the screenshots.
How did it happened:
I generated maps for seed reviews, so I can make videos of the seeds I found. I generated a map with a random seed (it was -4259845526421387129), and when I saw what did it generated, it reminded me on other generations, because it is not the first time, I already generated a square cutted map.
IMPORTANT: I tried to re generate the map, and it generated a similar map, but NOT THE SAME. I cannot fin any of those square buildings again, only on that map. (Another bug, or that is how to reproduce this bug)
Reproduce: Go back to your singleplayer worlds, click on your chunk failure world, and click "re generate".