I was able to reproduce this with the wheel off the bike and skewer removed, just spinning it freehand.
Turns out it only occurs when the axle is in just the right position. Rotating the axle slowly (left hand) and holding the cassette steady, I was able to find a position where the noise occurs consistently (as in the video). Rotating the axle a bit further and the noise goes away.
Decided to take it into the shop and they guys there believe it is a bent axle. They are also somewhat stumped because the cassette is steady and spins like butter, but they are going to open it up tomorrow and operate.
Thanks for the help!