Production shipment is btw now at 138.15 million whereas Unit sales (normal shipments) are at 136.32 million. The difference between those two methods isn't as big as it were some years ago, because the PS2 isn't produced that much anymore.
If I remember right the figure Sony was giving for the PS2 before was shipment to warehouse, not to retailer. Which mean it accounted for replacement unit and other that wasn't necessary sold to retail.
Not saying that the number here are spot on just pointing out that the number you give as production shipment vs unit sales(which I take you mean as shipped to retailer) is too close to one another. That or the PS2 was the most reliable machine ever or Sony just didn't replace the broken unit.
Persons without argument hide behind their opinion