Random bits of endstone appear in places they weren't before in the end

So basically, I've been working on a project in the end for just about 1 month now, it involves replacing the main islands end stone with grass and normal stone. How ever, I've noticed that whenever I save the world and close the game, or travel between portals, random chunks of endstone will spawn on the edges of the main land in places where the weren't before. Even if I brake them, or replace them with new blocks, they will just reset if I save and close the game, or use a portal. I've attached some examples below, but they may look bad because they were taken using my phone to take a picture of the screen capture on my switch, some are before and after photos, some show how even if I try to remove them, they come back, and one is to show just how random (and annoying) they can be. I do know that no one would've noticed this unless they were doing what I am with the end, but still, it shouldn't be happening in the first place. I hope this gets patched soon.