Having some installation in the nether at [0 ~ 0] I came across some quality issue with the world generator. As this was originally based on 1.15.2 the plan was to rebuild after the nether update (1.16). However, said location is now unusable for my purposes.

There is no question about changes one has to accept but in this example I basically get a wall through my cave which is also located at a chunk border (which makes it look more like a bug than an algorithmic change, right side of the relevant images).

• 20w20b: good condition
• 20w21a: wall appears and splits the cave in half
• 20w22a: wall remains, lava disappears (not really an issue), that's how it looks now as well

This cropped up in 20w21a (20w20b was the last good version).

world: 1.16 pre-release 2, large biomes, seed 24101970