Superflat Presets won't save

So I created a new flat word and did the customize presets. This worked the last time I did it, so I put in a preset. I pressed Use Preset but it just went back to the normal preset.

I don't know why. I've been trying for ages!

Please fix!

Thank You in advance.

EDIT- I tried on 1.12, and it worked, so I will just make the world on 1.12 then update later.