Pazon smartfire

I have been experiencing some starting and running issues with a pazon smartfire system.

The story so far; I started this project about 20 years ago and like many projects getting time and money to coincide was always an issue. When rebuilding the engine a MkIIA 1974 850, I opted
for the PW3 camshaft having read a Peter Williams account of it, I also decided on a Pazon Smartfire ignition system again following advice that it would suit the PW3 cam, purchased both around 2008.
Move forward some years to 2024 the bike was now all together and ready to run, all set up as per instructions and timed up, the engine burst into life and ticked over with a bit of carb twiddling.

Move forward to this year and ready for a test ride,difficult to start, re-set timing as per instructions, set off cover a few miles return home for a quick check over, a few hours later set off again but this time after about 5 miles a miss fire that then leads to an engine stop, scratch head 
look for loose wires etc check fuel, after 20 minutes give it a bump start down hill, it bursts into life and I ride home, just getting home another miss fire, check everything over again cant see any good reason for the problem.

Another test ride a day or two later exactly the same again, after a few miles miss fire and the engine eventually stops.
I have checked fuel supply, all good, fuel tank breather all good. All components are new from ignition switch to ignition and carbs etc.

I contacted Pazon who asked me to check the air gap between the rotor and the timing plate, I measured a gap of 6.10mm, far to high they said, it should be no more than 2-3mm maximum.
Now Pazon have changed their smartfire system so the new rotors and timing plates are not compatible with my module. They said increasing the thickness of the rotor could be a way forward, but were unable to explain why I'm seeing such a large air gap other than this explanation :-
"The air gap is likely due to the brand/type of camshaft.
We have seen this before, but don’t understand why there is this mechanical difference.
Assuming your points housing is standard, it points to the final taper end of the camshaft being shorter than standard."
So I'm baffled as why a PW3 would end up with a shorter taper than usual given the build quality of the product, also having rinsed the internet for answers I found one example of electronic ignition rotor taper being wrong and damaging and braking the camshaft taper, causing poor sparking at the plugs. I will be inspecting the cam once I have removed the outer timing cover to see what's going on.

If anyone out there has any helpful suggestions or has had a similar experience please feel free
to share your wisdom with me.