Just starting the deccond boil of my double brew day i have a twin element stainless boiler and well before it has reached boiling its started vibrating i tried in plugging each element singular to see if it was one of the elements but if it is its both as it happens on both of them, Has this happened to anyone else and is it safe to carry on? i have touched the boiler without thinking and didnt get a shock Any advice/ideas??