Shouldn’t be that way… I just finished dual moding my mad catz and cthulhu.
When you wire the inverter, you’ll connect it to the 360 trigger pads just as described in the padhacking thread. What I did, was I then ran my wires from my 360 to the cthulhu, A-H and 1-9 slots. Then the cthulhu to the buttons.
Both the cthulhu and the 360 register as no action upon pressing. Then if you use Windows to test your stick you can test the mad catz and cthulhu in he game controller area.
The mad catz registers the Z axis when you press the left or right triggers, then for the cthulhu they are buttons, I don’t remember which though.
The mad catz registers the Z axis in the center as neutral, then when one of the triggers is pressed it is low, then high for the other trigger.
Hope that helps, but I would say if he cthulhu is registering as pressed but your mad catz works, something is crossed on your wiring.