Computer generated trades is a possible explanation for so many at the same price but I do not know why that would not move the bid/ask. The end of the quarter is Monday. Is it possible that the MM's wanted to book a profit for this reporting period(possibly year end for them) and they were the seller of shares that they bought from the weak hands when the price was lower? The computer would know the amount offered at the ask and always request to buy a bit less than the amount offered so as not to raise the ask. Just guessing, we may find out and we may never know.