I have a ball mount rack. It’s a bit older and a bit fiddly with 3 straps for each bike. It did come with a plate to stop it rotating around but that meant removing the ball every time I used it because I couldn’t tow a trailer with the anti-rotation plate fitted. Have rarely had any dramas with it rotating, mainly due to not tightening the connector properly.
After today, I’m looking for a better alternative. It’s taking too long to load and unload despite holding everything from a 12” glider to a 20kg big w fat bike securely with only occasion minor rubbing due to poor loading.