Flat world chunks disappear after new version

This version has a lot of issues such as the skin pack issues, but this is just straight the worst thing

so in the new 1.17.30, old superflat worlds (made pre-1.17.30) have this issue that some of the chunks are corrupted, in a way that they no longer exists.

mostly chunks that had something on them or were loaded disappeared, and as long as i know a lot of people have this issue with their worlds.

this is really devastating since all of the people that had been working on projects, maps or anything on flat worlds is now destroyed, same with me, i hope this gets fixed.