SMART Drive Failure Predicted - Code: 3!

Saw this error on one of my 4Tb drives in EX2100 after upgrading to OS5 recently. The other drive is fine. Can it be repaired as HDDs are expensive? I have it 3 years now.

Screen Shot 43

Upgrading to OS5 is asking for trouble … Welcome to the OS5 club.
Is it possible to go back to OS3?

I don’t know… I will investigate at the weekend. Thanks WD!!