@nonstop I have many years experience with Pertronix with 3 different vintage cars, a '28 Chrysler 6, where there was no specific module available, so installed a pertronix unit with same polarity, voltage and cylinders, basically screwed it onto the breaker plate of the distributor, worked perfectly. A 6 voltage version on my '37 Dodge MC again worked perfectly and this '36 Airstream (12volt) until this issue.
With both modules acting in a similar manner, I don't think this is a module problem here. I did check the voltage at the coil (12.4) and red wire of the module, again same voltage reading, even increased the size of the wire to the module.
@Plymouthy Adams so what do you think is the issue here?