Why even mess around in classic mode?. Classic mode should be called child mode.. Anyways you definitely have a sensor issue if your falling at speed...it maybe user error but doesn't sound it.. After .5 mph you only need to be on one of the sensors..although you should stay on them both.. Are you using flat sneakers?
I don't wear a helmet, classic mode pushback reminds me to keep the speed down. If I had done this at full extreme speed I might not have gotten my hands up fast enough to keep my head off the pavement and might be in hospital with a concussion (or worse) right now. I assume anyone riding extreme mode is wearing full safety gear whereas I am not.
Was wearing flat bottom DC skate shoes "DC Court Graffik Men" at the time.