Why are these products with flaws? - Bravo Company AR-15 Enhanced Lower Parts Kit

I'm not sure why, but it sure feels like there are second-hand products on this store from flawed inventory as if its known about. My main complaint is the grip. Everything else seems to fit properly, but why is the grip so tight that it won't go onto any of my lowers? I have tried to put it on two different lower receivers and it shaves plastic off of the grip as I attempt to put it onto the receivers. Why are you guys selling products that have known defects? These products are obviously poor QC products that are being sold second hand, or atleast it sure appears that way. Now I'm a bit concerned for placing orders here as I'm spending a lot of money. If the products are going to be poor QC batches I will start shopping somewhere else.

The 1 star is because a product is being sold that has poor quality and isn't disclosed in the description that the item has flaws.

-Trigger & Hammer installed properly
-The grip is so tight that its obviously a bad part