TM consistently "fails" on new 27" iMac, anyone else??

Over the last 5 months with new 27" iMac 10.7.5 (i5, 1G HD, 1G graphics, 16G Ram) backing up auto every hour to a 3TB Seagate Free Agent, has reported "Failed check Disk Utility." That indicated an unrepairable Disk so got replaced by Seagate (very good about it). Talked with Applecare and got very little info but it may be out of that Advisor's ballpark. Now I am getting the same message and find it hard to believe I have received two (2) bad drives since in 20 yearsi have had only one other drive fail.

Fortunately, I am backed up to another 2TB Western Digital so no danger.

Has anyone experienced similar failures?

In the meantime I will use Carbon Copy Cloner to see if it is the disk or TM.

Thank you for any comments or help.

Ed