I always order multiple units from Apple just because of these kind of issues -- dust under the glass or pixel issues. In fact, i just ordered 3 refurb iPads the other day and they arrived yesterday. First one had a huge chunk of dust under the glass visible in casual use. Second one had horrible screen bleeding. Third one was a charm - perfect. I have done this probably six times over the years since 2010. Never had any quality control issues before then. If Apple isn't able to do throrough quality control, I'll do it for them until I get a satisfactory item.