

True, but it’s not clear to me that both drives are exhibiting the behavior and it sounds more like a copy between two drives. I wouldn’t rule it out and do think it is a possibility, but in my professional experience drives fail much more frequently than controllers.
It makes sense to me to test the drives individually, in another system preferably, using smart long test, which is non-destructive. Next test other drives in this system. If there are errors, try changing out the SATA cables, too. If you can shuffle the data off the drives, do so and then try running them through a secure erase in another system. A bad drive should fail the same way in another system.
My other thought for probably not being the controller is that 4TB is a very long time for a sustained transfer to fail on a flakey component. Also, there are no reports of other errors.







I’m suggesting either using the secure erase utility built into your efi if available or using hdparm and calling secure erase.
https://grok.lsu.edu/article.aspx?articleid=16716
I suggest calling these utilities with no other drives connected.