Ok, so no sooner than getting the bed pretty much level, I now have another issue! I'm trying to print the right hand tool holder from here: https://www.youmagine.com/designs/bigbox-3d-printing-storage-tools-nozzle-sdcards-nicknack-s-boxes and all seems reasonably well for about 10 minutes, a bit of minor lifting bu generally ok, then out of nowhere there's a sound as if something got caught (nothing visibly did) and the Y axis is then totally off. I cancelled the print and have attached some photos. I had just greased the rods before the print, and had even slowed the print speed to 40mm/s in Simplify3D when I compiled the gcode. Just really looking for some ideas for the most obvious things to check first?