a small update
I have modified the cam trigger to have a smaller trigger area with the purpose to give a voltage spike similar to the original setup.

I have driven the car with the new trigger, and so far it works fine.
still to early to conclude anything, as the fault was very intermittent, so wouldn't appear on every run.
but so far, at least it looks like I have not created any other faults lol
my theory is that this cam trigger setup is often used together with other engine management than the weber marelly, and therefore perhabs better suited to receive the signal from the bigger cam trigger. Perhabs this could be the cause (if my new modified setup is working that is )
It would be great to hear from some of the folks that actually sell these triggers, and to hear if they have had troubles using this together with weber marelli