I've been trying to create a Readstone Ready World for testing and it never fully loads... it gets stuck at different percentages and after that, no matter how long I wait, it never continues to load and I have to forcefully stop Minecraft using task manager every time. I deleted the world and created a new one multiple times but it still gets stuck. I even reduced the sandstone layer to 1 and turned off/lowered the visual effects, yet again no change.  I haven't tried all the worlds but the regular superflat loads just fine.