This happened with lots of freewheels, and usually just meant that their threads were machined slightly off-kilter so that they wobbled side-to-side slightly with each revolution of the wheel.
With a cassette hub, it means that the freehub body is not perfectly in line with the axis of the hub. The freehub body attaches to the hub with a 10mm allen bolt. The wobbling could mean that the threads in the hub body were machined at a slightly off-kilter angle. Or it could mean that the freehub body isn't tightened down properly into the hub, or was seated incorrectly when it was screwed into the hub.
I've had this problem before, and it was solved by disconnecting and then reconnecting the freehub body to the hub itself. To do this, you'll need to remove the axle from the hub, to get the 10mm allen key inside at that bolt.