Conflicting Disc Utility Details - Failing Drive 2010 MacPro Yosemite 

A TimeMachine backup attempt gave me an error message of a bad backup drive. Disk Utility shows -


  This drive has a hardware problem that can't be repaired. Back up as much of the data as possible and replace the disk. See an authorized Apple dealer for more information. 


Now, the back up drive was one partition of a larger drive. This is the alert when on the full drive. Each partition passes the disc verify test. The latest backup occured this morning despite the alert from TimeMachine, and the current status from Disc Utility. 

Question - Does this problem alert from Disc Utility make sense, that a drive fails S.M.A.R.T. Status but its 2 partitions look fine?
Disc Utility isn't always the best tool for something like this.
I would probably throw something like this at TechTool Pro, Paragon Hard Disk Manager or DiskWarrior* for a good 'second opinion'. 

I would also be careful &amp; make sure I had a good clone of it first - Carbon Copy Cloner

*DiskWarrior is extremely good with Time Machine drives, as they're always HFS+, but can't handle APFS &amp; doesn't deal with the entire drive like the others, only partitions.
I've had TTP fix things DW couldn't &amp; HDM fix drives containing Windows partitions that the others couldn't - so there is no clear 'winner' between these three.
TTP contains SMART monitoring software too.

If I could only have 2 of the 3, I'd go TTP &amp; DW, probably in that running order.