Hello Bill and All,
I am reporting back to reveal what the problem turned out to be.
It was the diode RS1M (1N4442) that was intermittent. It provides the VCC for the Smart MOSFET chip.
One tends to measure these diodes last because it requires the disconnection of the transformer winding!
I did not have an SMD replacement but there was enough space for an axial diode of the fast recovery type.
[video|5949]
I hope this inspires others to keep going until the job is done!