The AH was indicating that the aircraft was rolling completely around the longitudinal axis about 4 times each second - hence the calculated roll rate.
It had failed - I'm pretty sure it ended up just lolling about when it stopped spinning - I can't remember for sure - it did happen about 15 years ago. It's funny the bits you remember - I could show you on a map where it occured within a radius of a about half a mile - I was climbing at the time - possibly in a shallow right hand turn.