Beats me, must be something different in the circuit or sensor.. Maybe they copied the syncro spark from C&H...If the old Zenoah cap is bad you could try taking it off the wire, then pull the shield braid back and connect the end of the inside wire to the spark plug..connect the braid to the engine block with a short piece of wire and try running it that way....I have run 3Ws that way on my test stand when the cap has been destroyed in a crash, just can't fly a plane with it....
My 3W twin test ignition is an old crashed unit..Exactly that setup witn NGK bakelite resistor caps on the wires and a ground wire with a spring clip on the end to connect to the engine..Works fine....
Try moving the sensor as far counterclockwise as it will go in the slots, maybe retarding the timing that way will work...