Driven crazy by the electric toothbrush

I’m actually of the opinion that an electric toothbrush stops automatically after 3 minutes of use. I even think I read it on the packaging when I first bought the new toothbrush at the beginning of the year. But this time I’m using it for a slightly different purpose… I wonder if that’s why it’s so overzealous this time that it just won’t stop scrubbing?! Oh dear… oo