Caves and cliffs

I had a superflat realm that was going to be a server, it haf minigames and all that, i turned on caves and cliffs a little while ago and when 1.17.31 released half of my world chunks were erased. My guess is that it tried spawning the chunks below zero, but because its a flat world it was deleted. I ttied resetting it to a different state before it happened but any version of it woth caves and cliffs turned on had chunks deleted