Ok finally on track .. boiler dead again this moring .. slight tap on
microswitch part of - diaphragm switch and boiler lit .. working
normally again

Operating hall thermostat .. can see the actuator arms moving .one had
a barral on the end and the other seems to have a 1 inch tapped rod
with coil spring , part of switch ..

.. seems the 'far' one ie the one that had no spring . moves initially
full travel then returns slightly in a slow 'damped motion' the sprung
one simply moves leaving the actuation arm behind ..

the question is .. there seems to be adjustment for travel .. but
what is the criteria ?

i assume the switches actuators are just on the edge and slightly
reducing the travel clearance will solve the problem .. ?

Tnx

G .