I tried to make an edit of this model https://imgur.com/a/KlZ4kJ0 it worked and looked fine in pmx, but when I loaded it into mmd this happened, I used the scaling thing in transform view in pmx to make the breasts bigger, HELP
Did you make sure that part's opaque is set on 1? If not, check your morphs.
Try moving her around in MMD. It is possible that her breast physics are caught on something.