Drive Suddenly Unmounted

I have had a 5N for exactly three years. One of the two 6TB Seagate Ironwolf NAS drives I bought at the time suddenly unmounted and the Drobo reported no disk in the drive bay. All of the other four drive bays are filled and all the data was rewritten.

I removed the drive from the Drobo and installed it directly to my computer. I used SeaTools for Windows and ran the “Long Generic” test. The drive passed. I then partitioned it and formatted it in Windows 10. It reported no problems and it is now and empty 5589.01 GB drive.

Is there something wrong with my Drobo? With my drive? I don’t want to put the drive back in the Drobo just to have it fail again.

There may be some answers in this thread regarding Seagate drives & Drobo:

Thank you for the help.