Another tip: for me it clacked audible after 5 minutes of exercise. It turned out that I had one of the pedals is not drawn correctly determine which then clacked at the highest point. Tightened screw, no more rattling. Also, the detent rod has rattled that one but only needs in the folded state. So, remove the stop bar, then also no longer the rattles.
The device is so what of quiet that I have even heard that one of my Scchnürsenkel-ends touched the frame when pedaling while clicked ....