IDEA: Ask your receiving people about returned goods: they are fully aware of your worst products.

Interview and train receiving personnel about checking incoming goods, returned products from customers, problems from boxes or containers opened later, priority receiving (i.e. receiving broken equipment parts, critical maintenance items). They know all of your bad products because they receive them back constantly.   They may talk to the drivers and get feedback what is wrong with your products. They may know problems with the materials purchasing is currently buying and problems with packaging or quality. Make sure you define what information you want them to convey every day.  They are first generally to see customer problems.