That is the oddest thing and you say 3 of your 4 corners have the same tear in them? There are no minute tears anywere else? I can't even begin to guess how this could have happened. It seems to me if the fabric was defective in someway there would be tears/rips in other places and not just at the corners of your binding. Being right at the corners and looking like you were doing a mitered corner binding, I am wondering if the fabric is getting caught on your sewing machine or something on your sewing table when you remove the quilt to miter the corners. Very odd and not sure how to solve the issue either. Sorry I couldn't be of more help.