I just thought I'd post this here for anyone else has been on the leading edge with Firmware and RC6 or BugFix. I noticed that my BB was losing it's mind seemingly sporadically as far as where the bed was with RC6, mid-air printing and the like. I've identified at least one core cause of this is that RC6 decides to stop using the mesh bed level information if you home axis independently. E.g. G28 X Y or G28 Z. Which just happens to be what is on the Control screen in OctoPrint, so yes, I use them occasionally. (Note: Don't home Z first when you are in the dock, bad things could happen). In any case, this ticket opened up in the Marlin branch that helped me identify the independent homing as at least one cause: Marlin#3750 As a result, to work around this, I've added this to OctoPrint "Before print job starts" GCODE Script. You could add the same to Simplify3D if you use that and print directly, I wanted it to work if I also print random gcode off SD. G28 ; home M501 ; load eeprom G29 ; check mesh enabled Marlin RC6 (somewhere between here and stock) also introduced blinky X Y and Z on the LCD that alternate with ? if they have lost their reference. I'm noticing that mine seems to lose Z when my print is complete. I haven't identified the cause yet, but still looking into it. The G28 before printing makes this ok, but still like to understand why it's deciding it's lost it's reference of Z0.