Another Issue: extruders do not grip the filament well enough, resulting in low density, poor quality print. There is no tension adjustment on the extruders that coming with the M201, so they're not fit for purpose. In the short term I have increased the spring force by forcing the spring coils further apart with a horizontal screw or two, which is a horrible hack, but at least the prints are ok. If i persist with this printer i'll replace with extruder filament drives with something better. The extruder motors seem ok.