you sound like me!!! thungs to check on":
the adjusting wheel at the cable is slightly off.?
the pushbutton mechanism needs t be cleaned and lubed with spray silicone ( what has been recommended to me)
the pushbutton is missing / broken part?
the adjustment for the pushbutton vs a floor shift is different, that is the position you start at.
hope this helps.
there are other methods to adjust he sucker. I forget where I found them now.