Fill command not working in negative y coordinates as expected

So by the title you will assume this is a different bug from 1.16, but that is a mistake. This time, it is refusing to use /fill in coordinates under 0. I have never had this particular issue before. I have tried Y=-60 to -61 and -63 to -61 to destroy grass and dirt for a race track that takes place over the void, but it would not let me. This is very annoying to deal with because now I will have to destroy over 100k blocks by hand with a third party controller and pray I don't break the actual course itself