Hi! I bought a used Fischer Proline 1401. There seems to be an intermittent fault in that when it’s being ridden the assist doesn’t kick in at all although the motor can be heard. However when the bike is turned upside down for inspection the assist DOES kick in but most of the time at a lower level than the one set. I’m a total novice with these bikes so would really appreciate some advice. I don’t have a ma