Unfortunately it is a common thing. Not only on BW bows, but on many others too. As I understood it, there is only one glass supplier and that is Gordon's. The quality sucks and that is a pain in the ass for customers as wel as for bowyers. The cracks are caused by small bubbles or imperfections in the glass fibers which will cause cracks in a later stadium. It is for bowyers impossible to detect those bubbles.
As long the cracks are parallel with your limbs, it is only cosmetic and it won' affect your bow in any way.
I hate it, but it is the reality we have to live with, thank you Gordon!