I have an '02 52" Hydro Scag & it won't track straight. I continually have to mess with the black plastic knobs that adjust the tracking on the right & left side. I have noticed that on newer Scag models that there is just a nut instead of the black knobs. I am alone in experiencing this?....It just seems that the knobs vibrate too much from the mower & mess with the tracking. Should I just take em' off & replace the knobs with locking nuts?