Every time same error

I have My Book Essential 2Tb.

When I do reformatting disk it looks ok and I start to use it for Time Machine backup. First backup (about 500 Gb) usually done succesfull but next sessions ends with error message then I start to verify disk in Disk Utility and always see the same strings:

Verifying volume “Backup”

Checking file systemChecking Journaled HFS Plus volume.

Checking extents overflow file.

Checking catalog file.

Checking multi-linked files.

Checking catalog hierarchy.

Checking extended attributes file.

Checking multi-linked directories.

Checking volume bitmap.

Volume bitmap needs minor repair for under-allocation

Checking volume information.

The volume Backup was found corrupt and needs to be repaired.

Error: This disk needs to be repaired. Click Repair Disk.

After that I repeat all operation (formatting and full backup) and face this problem again and again.

So I suppose there is perhabs two problems:

  1. Disk corrupted

  2. Power supply issue causing controller problem

Is there any way to detect problem exactly?

The drive is corrupted

you can try first aid but the same thing might happen

replace the drive if possible