CHECK THE MICROSWITCH. I thought it would be evident. The plunger comes out when hot water is demanded but no boiler operate sequence. CH if on is running the system and during that cycle you get hot water, there fore, I would be checking to see WHY no operation for HW when plunger does push the microswitch.
Above applies if 60 degree light not relevant
First thing I checked was the microswitch, it works fine.