lol funny but still doesn't explain why the odd rotation or spinning.
I don't have any full-fledged answer to that - questions like these are exactly what I'd like to see answered or at least discussed (potentially in a sci-fi context) in here.
For what it's worth, though - the object, whatever it is, does tumble according to all the data we have. If this sort of tumbling motion is something that can occur naturally, then it can also simply happen to an artificial object (by accident, or because the Klingons used it for target practice, ...) - or it could be something the object does on purpose (artificial gravity? acceleration control? ...) - or a combination of several causes.
What I currently wonder is if this motion has been taken into account for the approximations of object mass and density in the published paper? If the object tumbles randomly (which means that it doesn't simply rotate around one of its major axes), then its biggest surface wouldn't always face the sun, and in consequence the force exerted on the object would only be a fraction of what it could possibly be.