Why do some of my disks get errors during certification?

If some of the disks you are certifying are getting errors, there are two possible explanations:

You have an unreliable batch of disks. Some manufacturers ship new hard drive technology before it is truly reliable. We have found this to be the case with early shipments of 6 and 8 TB disks. We have also seen this occasionally with refurbished disks.

Your Mac has a hardware problem. Some of our users have more than 50% of their disks fail certification. We have found that this is most often caused by bad or mismatched RAM or other hardware errors. You can test whether a Mac hardware problem is causing your disks to fail by moving your disks to a different Mac and re-certifying them. If they all certify successfully, the most likely explanation is that the original Mac has a hardware problem.

You can further diagnose this problem by removing all 3rd party RAM from the failing Mac or running the Apple memory test.