The first answer is a great one.If that doesn't show the problem I would get an IR heat sensing tool and shoot all of the lugs in your system. I would certainly not invite your electrician back. They sound like parts changers. From what you have stated the problem is "up stream" from your pumps and the breakers. If in the same leg on all breakers has been failing back track the system and find the loose connection or deteriorated connection. There must be a commonality.

This problem can be resolved with a good control or boiler technician and about 2 hours of research and real troubleshooting.