Steps to reproduce:
 - Make some worlds in 1.17 and load all chunks within a a specific render distance (don't move)
 - Update to the newest prerelease and find the border
 - Go along the border and you will sometimes find this
Or 

• Set your render distance to 16
• Make a 1.17 world with the seed 9184991237633477144
• Look arround (don't move) to load all chunks
   - Update to 1.18
   - Use this command
  /execute in minecraft:overworld run tp @s 119.19 125.93 -273.52 -794.55 23.85