The "switch machine" in the 223 is essentially just an AC solenoid. But since it needs to be a "double throw" (i.e., to be powered in each direction), and since AC current can't be "reversed" like DC, you actually need two solenoids, end to end, with the coil on each side wound the reverse of the other. The controller then directs power to one side or the other of your "double" solenoid. The "double" solenoid has one lead in the center which is common to both coils, and then each coil has its own "outside" lead.
So on a DC coil, if the coil goes bad (burns out), the switch will not throw in either direction. But since an AC solenoid has 2 separate coils, one can burn out while the other is still good.
If you are hearing no buzz, no chatter, and the switch consistently throws one way but not the other, then one "side" of your double solenoid is dead for some reason. Either it is not getting power (the wires or connections to that side are not good), or the coil on that half of the double solenoid is itself bad. This can happen if the controller is held for too long: these are designed for "momentary" power to throw the switch and then immediately be released: steady power for longer than a few seconds will burn out the fine wire used for the coil. But be sure it's not the connections and wires going to that side of the solenoid first, before assuming the worst.
If you have a continuity tester, you can check each coil by testing between the "center" lead common to both solenoids and each of the "outside" leads in turn. You can even do this by connecting the tester to the terminals on the top of the switch - the three control terminals, not the aux power terminals. I suspect you will find one side has lost continuity, i.e. the coil winding has a break in it.
david