Passport 2TB randomly switches to Read Only on OSX

WD External Drives WD Portable Drives
1

I have a 2TB Passport, formatted in Mac OS Extended (Case-sensitive, Journaled.)

It is attached directly to a MacBook Pro retina without a USB hub, and over the last few weeks randomly switches to read only until I eject. unplug and then plug it back in.

Any idea what would be causing this?

Thanks.

2

Have not seen this before.  Have you tried in another Mac? Do you receive the same results?