I ended up having to replace my hex hotend after a heater fail. With my arm in a sling I did the job with well one hand, not fun but it lead to a discovery on my machine. I have had minor and fully unexplained Z variations, random and never the same when printing the same model. I called them micro layer shifts, as they were really minor but easy to notice. On my extruder gantry I tried new bearings as the old had a good amount of play, and one started to click. Tried Igus which were not good for the 6mm rods, and some off brand that I could find in the right size. Went back to the factory bearings with two wraps of blue tape on each bearing. This helped, the clicking went away and the prints did look more consistent. Still had the random layer shifting. Hotend fails, take it apart and install the new one which Robo was quick to ship. As I am holding the hex with my thumb and trying to line it up to get everything tight, I started to notice it would take a new angle if I bumped it. Started to think I was not getting it set correctly - Ran a print anyway and noticed any area that caused more friction (switching infill patterns for example) would change the angle, if it hit a rare blob that would do the same. Broke the extruder assembly down after I broke the bolt that holds the hotends. I thought I am going to get this as tight as possible and see, and still had the movement. Finally snapped it. Putting the aluminium plate on glass and setting either hotend into the slots and I still get a fair amount of play. By fair amount I am mean visible without needing tools to measure. V6 hotend is really snug and won't budge. Anyone else ever check this? Since both of my hex hotends have this play, I wonder if the factory plate is flawed and out of tolerance. Thanks for putting up with my one armed typing, can't wait to get this sling off.