The Twist and Stow rudder needs to be cleated down. Pull the down line and with tension on it... place the line in the cleat. If not, the rudder will strat to come up a bit and as it "twists" it causes a left turn.
It is possible that the rudder, when hard over, would have a loose control line on the opposite side.
We have a rudder manual here: http://www.hobiecat.com/support/articles/archive/?src=http://2010.archive.hobiecat.com/support/tech/Twist-n-Stow_Repair_Manual.html
I suspect that you have a newer model MirageDrive. More recent drives have threaded masts that thread into brass fitting molded into the sprockets.http://2010.archive.hobiecat.com/support/pdfs/Mirage_Drive_Parts.pdf