Unable to create custom superflat worlds

I can enter the text part in to the input field, however when i click "use preset"
it reverts back to the last pre-clicked customization.
example: I enter the text

3;1*minecraft:bedrock,20*minecraft:stone,10*minecraft:air,60*minecraft:stone,7*minecraft:dirt,1*minecraft:grass;1;village(size=10 distance=5),mineshaft(chance=5),stronghold(chance=5 count=4000 spread=3),biome_1(distance=32),dungeon,decoration,lake,lava_lake

and click "use presets", then it displays the menu for classic flat.
if i click on redstone world for example, it will show the menu for that code just fine.
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