Cooktop Won't Boil Water

I am having trouble getting water to boil. On occasion when it will boil, I add the pasta or what ever I’m cooking & the water will not go back to a rolling boil. (left rear burner).

The front Right burner will boil only to the tiny bubble stage and that is after more than 45 mins at which time most of the water has evaporated.

I have had two separate repair companies out. The first one didn’t even look at or test the burners. He said that what I was saying was impossible.

The second took out some sort of laser and tested all burners. They all heated to well past the boiling point. I placed a pot of water on it and it would not boil. I placed a smaller pot and it boiled. His recommendation was for me to buy Stainless Steel cookware as Calphalon and Chantel were made for Gas cooktops. He also suggested that I put my posta in the water before it boils.

Any ideas?

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