I had an awful creak (sounded like something was going to snap). It turned out to be the freehub. Check to see if you can wobble the cassette. There were also witness marks on the axle where the lockring was rubbing under heavy load.
I had this error. It was confirmed as a code that is thrown when you turn the bike on whilst in motion/riding it. This ties in with the abnormal behaviour of the motor I experienced when I turned the bike on after turning off a canal path and heading up a hill. Only turn the bike on when...