I have a world since somewhen before Update Aquatic. After one of recent updates I had a crash with message that the world is corrupted. I reopened the world immediately after, and found that new terrain had generated over my build, replacing entire biome with river. Part of my build (bridge) was right on the edge of biomes and got distorted by blending. Hundred blocks to the left and to the right I have my old world with my builds, but the middle got overridden. My last backup with world intact is from November from the day 1.18 was released. I can provide a copy of my world if needed, with coordinates.