Fairly new kettle, Morphy Richards pyramid shaped.. Every so often ( usually if you are out of the kitchen of course) the kettle boils and boils and boils and does not swich off. It is correctly filled between the max and min mark. You dig out the warranty and the box and of course I just tried it again and it works perfectly 10 times out of 10..
I've a MR kettle and exactly the same thing happens! Mine eventually switches off, (leaving clouds of steam in the kitchen) I've descaled it since, and, so far, its behaving itself. (It was only slighly scaled) Mind you I've also told it that I've seen a new kettle in Currys!!