Popcorn machine mains problem

A popcorn kettle on the bench. It was reported to trip mains fuse. When testing it I measured 1.3 kW. But kettle was marked 500 W. I opened it up and could not see or measure anything faulty. Cables and grounding was good. But there were rust on the thermostats nuts. I cleaned the nuts and rusty residue on the thermostat. Put everything back together and now the kettle measure 500W and the thermostats works. Is it possible that the thermostats was faulty due and the reason for it to draw 1.3 kW instead of 0.5kW?