.i think explains it.

From an article by Dr Aniruddha Malpani, MD:
"The third group is perhaps the most difficult. These are women who grow a sufficient quantity of follicles in response to superovulation ; and have high estradiol levels as well. Egg collection is usually uneventful ; and the doctor often retrieves 8 to 16 eggs for them. If IVF is done, when the fertilization check is performed the following day, much to the embryologist’s surprise and the patient’s dismay , it is found that the fertilization is very poor even though the sperm are fine and actively motile. If ICSI is being done, the embryologist often finds that the eggs are morphologically normal ; or are very fragile. For example, these eggs have granular cytoplasm ; or vacuoles in their cytoplasm ; or dark areas within the cytoplasm. Since normal eggs are simple spherical formless blobs, these subtle cytoplasmic abnormalities are often missed or overlooked. The embryologist may also noticed that the eggs are fragile, and the cell membrane offers little resistance to the injection pipette. Many of these eggs may die during the ICSI process.
Unfortunately , because egg morphology has not been adequately studied , we still do not have good descriptive terms , when talking about these abnormalities. Since the eye only sees what the mind knows, often these abnormalities are not picked up. The patient is often subjected to repeated IVF or ICSI cycles , with the same poor results each time."


we're just a "hard egg case."