I decided to try Emmett Lalish's tricky Pre-assembled Spherical Iris box ("not for the faint-hearted and needs a well-tuned printer") on both my trusty old Mendel90 and my new E3D BigBox. Taking it slowly, it's a 10-11 hour print at 0.15 mm resolution, so I left it running overnight. The Mendel90 did well although a little over-extruded, meaning I haven't been able to get the mechanism to work yet. The BigBox however, presented me with this mess. No signs of over-extrusion - I think the mechanism would have stood a much better chance of working on this copy - so no real clues as to why there should have been such a sudden and dramatic shift in the Y direction. This is becoming an all too frequent occurrence lately, and I believe the shift is usually parallel to the Y axis. Anybody care to suggest what may be causing this?