I don't use a scag. But I have been using hydro's for 10 years now. I have never had one come out of alignment by it self. I have tried to adjust mine and put it out of alignment. Try adjusting the threaded rods on the sides of the mower. Mine are from the T bar to down by the hydro pumps. It is on a Toro though. I think they are all about the same? Yours should be from the pistol grips down to the Pump area. Just do a quarter of a turn at a time with the blades off. Try only the side that it is pulling to. If it makes it worse then turn it the other direction. Stefan