I'm using a brass nozzle with extrusion multiplier set to 0.9. Added a sharpie line across the gear/shaft. Just ran a test per your advice. Removed the fan and hotend so it's just the extruder gear. Used OctoPi to extrude 100mm of filament and only 79.2mm came out. No gear slippage. How is this poss...

I got a new M2 Rev E a few weeks ago and I've had a bizarre underextrusion problem that I haven't seen anyone else document (I've pretty sure I've read every extrusion related thread in this forum and other printer forums). When printing a thin 20mm wall cube (Slic3r Prusa Edition, 0.2mm layers, 30m...