What kind of drives are they? I swear by western digital green and red 4500 rpm drives. I've never had one fail. 7200 rpm drives just aren't reliable enough for important data.
Also, how are you formatting your drives?
I tried to format a 2TB drive once using an old USB to SATA adapter. It appeared to format correctly, but it wasn't working correctly. Turns out that the adapter didn't work with Advanced Format 4K sector hard drives or something. Or maybe the drive was too large. I'm not sure.
I later connected the bare drive to an internal SATA connection in my primary PC and formatted it that way and it worked as expected.
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