I had one of these and it worked great, until it didn't
The rotatory mechanism froze and it grabbed onto the ring of the mooring ball, but would not complete the rotation and I was leaning over the bow, now holding onto the device which was stuck on the ring. I cannot remember how I got it dislodged, but it nearly caused me to go overboard as I struggled to get it loose.
I took it home and dismantled it. There was debris, which looked like dried sea water encrusted into the ball bearings that were used to facilitate the rotation.
Lesson learned is to check the device before you leave the dock to make sure it works, and probably to wash it down when you return. Finally, it may need some lubrication periodically.