SMART OK, Quick Test/Fill Diagnostic Failed!

I have a " My book Essential" 1 TB external hard drive. Recently I had issues with the same where i couldnt read the partition. I ended up taking a back using “Recover My Files” and then formatting the drive.

After that I set up my drive again. Then I found an interesting tool for the health check on the drive. I did the SMART run and it came out ok. I did the rest of the two " QUick Test" and " Full Diagnostic Run"…they both ran for few minutes and gave the message the Test has failed. I almost lost my data one time and I really need to understand how to fix this drive so that the test doesnt fail.

I am worried as I bought this to be able to store all my personal important information and I am not comfortable putting on this drive unless I am sure it’d not crash on me again.

This is simple.  The hard dive within your NAS IS failing!  You need to, as a matter of urgrency, back-up all the data you wish to keep and send the unit back to W.D. for repair or replacement.