You seem to be a Bosch component seller. Which M2S bike did you get ?
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Have you checked your rear axle hasn't come loose ? Would explain both the rattle and speed sensor error. Loose rear axles was a common issue when the Amflow first came out. It was the first bolt I put a Torque Wrench on. Though there was a speed sensor issue as well, which was resolved.
Doddy just did a video with Rob about the Mondraker. Those bikes are assembled at their European head office and the quality control is very thorough. Doddy would be very interested to hear these issues you are having. I would take it straight back to the LBS.
Iain Richards bought the same bike and has posted videos that he is having a very positive experience.