LT6656 testing

More than 10% yield loss due to out of spec references. How is this possible since Certificate of Compliance claims each part is individually tested? (I have thoroughly reviewed the datasheet and applications notes, and have taken into account potential stress due to soldering and/or reflow temperatures (SnPb profile used)).

Part LT6656-BIDC-3#TRMPBF

Analog Devices Lot Code 1506

Direct Customer: DigiKey/Date 10/19/2018 / AD Sales Order Number 1000378728