Any time a product has multiple failure in a point like this, in this case a narrow part of a glass structure, it is a design defect. These are all in exactly the same place, right in the middle above the nose.

It should be obvious that the location of the crack is where the glass could bend when the sides are pulled in to fit the person's face when the straps holding in on are tightened. Clearly they allow that area to flex too much for the materials used to hold up.