Mybook 20Tb Failed extended test

Hi Guyz,
i wonder if anyone can advise I have just purchased a new WD My Book 20tb, I downloaded data lifeguard as recommended to test the drives, it passed the smart test & the quick test, but failed the extended test saying too many bad sectors, am I right in thinking this drive needs to go back to amazon, i have run chkdsk on it and it found the MFT table was incorrect, and it said to run chkdsk f to fix it, but if its faulty id sooner just send it back for another one, thank you for any advice