bosch rotak mower motor seized

[atrier]

My rotak 40 mower trips the house wiring before even starting. It worked well last time out. The booklet mentions a "safety cut off " with a reset device. I can find a temperature sensor on the outside of the motor but wouldn't this just cut off the current if the sensor was faulty (not trip the wiring?) There is a friction brake stopping the motor turning. Is there anything internal that switches this brake on and off?
all help gratefully accepted.