Minecraft wiki entry for Development_versions, associated text: MC-241774 – Crash when going nether portals or creating a single biome world with nether biomes // java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0.
MC-241775 – Crash when going through end portals or creating a single biome world with end biomes // java.lang.NegativeArraySizeException: -5.
MC-241778 – Game crashes or freeze when loading and upgrading the 1.17.1 version of the Superflat world // java.util.concurrent.CompletionException: z: Biome decoration.