So, did a bit more experimentation: My motor VREF setting is 90 for X and Y. I was printing at a peak feed rate of 90mm/s and 130mm/s travel-only speed. Object sliced with Cura 2.1.2 and acceleration in Sailfish firmware was limited to 300mm/s^2 for X and Y. I notice that occasionally, acceleration is ignored and the print head races to its next starting point at the full 130mm/s travel speed! This results in a "bang" and the stepper motors skip and printing continues at a new location killing the print. I did some reading here: http://www.sailfishfirmware.com/doc/sailfish.pdf (READ SECTION 9.4). Sounds like Sailfish cannot "accelerate" a move if it doesn't know the last location (e.g. last location not saved in EEPROM). I wonder if Cura 2.1.2 does something to the gcode that could cause this "NON-accelerated" move phenomenon to occur randomly MID PRINT. 130mm/s without acceleration on a dual direct extruder Cartesian setup is painful to watch.... I am sure my 90 VREF setting is also reducing the amount of holding torque resulting in the steppers having insufficient force to overcome the momentum of a 130mm/s un-accelerated move - resulting in skipping of steps. thoughts?