Passport intermittent ejecting

Passport 2TB USB3, on Mac OS 10.8 MBP, bought just 3 mons ago been working fine.  Formatted as NTFS, just readable on Mac.

Started to eject by itself - sometimes it still shows as mounted but can’t browse or see folders / files.  It seems likes its fine until I start doing some heavyish data transfer from (or to) the drive.  Files all look like they’re there but haven’t verified.

What can I do to test where the fault lies and get a fix?

Also, in Win8, ran a Check for Errors, and downloaded the WD disk utils and ran a Quick Drive Test and both are ok.

Started to copy some files off and the drive ejected…always mounts / connects fine after I re-connect.  The file copy operation threw up a dialog of course as it ejected half way through the copy.  Reconnected and did Try Again and it continued to the end.

Another piece of data…once got a Mac error code of 36 when transferring files.