Divinorum wrote: I was told the door knob has never been serviced
They lied, possibly they didn't know that they lied, but they did.
What had to have happened. When it was taken apart some of the springs/pins got lost and whomever was working on it made do with whatever they had. The Top (silver) spring is the correct spring and the bottom (T) pin is the correct driver pin. There is suppose to be five of each in that lock.
Anti-bump pins with stronger springs (Ilco makes them) won't work in a schlage F series with the compressible spring caps. It would push the cap right off.