These really had me scratching my head for a few days.
As you probably already know, both must be pressed at the same time for the switch to work.
I had problems after checking continuity through the switch, in that even though I was getting the proper meter readings for each wire pair, I only had either nose-up or nose-down trim no matter which way I pushed the switch.
For some reason, polarity matters with this switch. After trying a couple of different re-wires, I finally got them working as advertised. The switch in the 727/737 is a sealed unit with the wiring diagram printed on the switch body such as is pictured in the maintenance diagram above.
Hopefully, yours has the diagram.
The strange thing is, I would suspect a diode matrix within the switch for it to act like this, but it is not pictured in the switch schematic.
