Then, I would try the DBAN software to do the low level format, once it completes try running the diagnostic again or can contact Seagate about an RMA.
I can't accept defeat easily, so that's why I would do the low level format before attempting to RMA, but that's just me.
It might not work since the diagnostic wouldn't run all the way through.
Please keep us posted on the outcome regardles of the path you choose.
http://www.seagate.com/www/en-us/sup...ns_assistance/