World Gen / Optimize world from 1.9.4 to 1.20.1

I have the problem that Minecraft reports a faulty world when I want to optimize / update the world from Minecraft version 1.9.4 to 1.20.1.

Before that I only played with Oh The Biomes You'll Go. Updating a map to a newer version was always possible.

How do I update the map from 1.9.4 to 1.20.1?

Is this error / bug already known?

or is it not possible at all?

Tis is not At all possible due to the massive backend changes and changes to the modid