Drive failed but still formats/checks OK outside Drobo

A few days ago my Drobo5N (all slots filled, single redundancy) notified me that one of its 5TB drives had failed.

I replaced it with a new drive and everything is back to normal, but just for fun I stuck the “failed” drive in a USB3 enclosure I have lying around, and it takes a format and passes a disk check just fine (this is on OS X, for what it’s worth).

I don’t need to put it back in Drobo, but I’m wondering, is the drive actually OK to use or should I still consider it junk?

Drobo seems to be more “sensitive” to drive issues than a standard disk check would show. I would continue using it as a separate “stand alone” drive… like your USB3 enclosure for instance.