Loose connections cause unscheduled down time.
hydrogen boiler infrared thermal imaging hydrogen boiler visible light
Infrared Thermal Image Visible Light Image
This is a loose or corroded connection on the line side of the contactor. This should be corrected ASAP. It will eventually get hot enough to melt down and cause a direct electrical short. From there it is no telling what colateral damage will be done. But the machine will certainly be down for a good amount of time.