I just got my evaluation back. There's definitely something wrong the way you guys are sending, either the stamping or signature is not correct, or the seals are tempered, there's simply something getting wrong. I followed the same set of rules, sent the documents to WES, and they have evaluated on them.
Now as they have, HEC sealed envelopes from many other previous Pakistani applicants like me, they know exactly how sealing is done. So if there's something that is different, they'll surely ask you to fix it.