They do 6 full 360 degree turns, before turning 180 degrees the other way.
That sounds like you have a servo that has been modified for continuous rotation. Unmodified servos are unable to travel more then around 180 degrees maximum. That means it is no longer a servo but rather like a simple bi-direction variable speed geared motor. As such you need to rethink what your servo commands will actual have the 'servo' do. You no longer have any means to precisely control where it will stop.
Lefty