This is a common problem ive seen recently, two ways to fix this ..1. Try using the auto dress feature to undress all.. 2. Get naked and die, another player having similar issue found that taking off all armor then having a fight helped "kick" them from the saddle which is something common that naked hunters also experiance. If neither of these option work for you, then I recommend contacting support or find an admin when they are online and they can fix this for you