3TB western digital wd30ezrx gives error on full format

Hello,

2-3 days back i purchased 2x3TB drives and before starting the data backup thing i wanted to make sure that both drives are fully flawless, so i ran a couple of tests on them.

i ran these tests.

1. Data Lifeguard Diagnostic for Windows (from western digital)
i ran quick and full extended tests on both drives and they passed

2.Seatools (from seagate)
ran Short DST tests on both drives and again they passed.

3. Quick formot
both drives got formatted in a single 2.72TB partition this way, so i say it was fine too.

4. Full Format
one of the drive successfully completed this task too but when i ran it on other drive it showed me error saying "Windows was unable to complete the format"
i tried this format again and again but nothing worked it showed me the same error again and again.
i noticed that when this error appears the drive gets ejected from device manager list and from "My Computer" so i need to scan for new Hardware in Device Manager to make it appear again......i have also tried switching this 2nd Drive to that other Drive port which passed the Full Format, but same error showed up......so please guys tell me if its a windows error or something else(bad HDD)   so i won't loose my precious 3TB of Data.

Thank You