Well here is the interesting thing. I used a different plane today and experienced the same issues BUT, the esc showed the error when the problem occurred. Note I was deliberately forcing lots of power through the system and blanking the airflow over the esc.. The ESC cut off at 100 degrees C, as it should. I could replicate this very easily on the ground and by connecting the Jeti box, watch the temperature rise as I increased the throttle. At 100 degrees Bingo the motor cut and as the temp of the esc dropped below 100 it became active again. The jeti box also logged the error as T = Y So far so good, it was just as we expect. ON the other model, exactly the same symptoms BUT the esc never went above 85 degrees and no errors were logged. I think it is clearly a temperature issue as it has never happened before and 32 degrees C in the UK is most unusual. I have checked all connectors and it happens with both new and well used batteries, as the Hacker is very old and very well used, to be safe the motor is out and off to Hacker to be overhauled.