I'm having the same problem too. I just tried to upload a world that was too big, so I went into the regions folder and deleted some of the chunk files and tried to upload it again, but now it's giving me this error. It still works when I try to upload other worlds but just not that one. I've tried to put the regions folder into other world saves and I can go into them in singleplayer just fine, but I still can't upload the world.
Minecraft Atom
I'm having the same problem too. I just tried to upload a world that was too big, so I went into the regions folder and deleted some of the chunk files and tried to upload it again, but now it's giving me this error. It still works when I try to upload other worlds but just not that one. I've tried to put the regions folder into other world saves and I can go into them in singleplayer just fine, but I still can't upload the world.