When I am printing calibration cubes (still busy calibrating the printer after upgrading), after a while the extruder starts skipping steps and cause under extrusion. My Setup: Wanhao D5S Mini (upgraded to DuetWifi, E3D v6 hot-end [3mm version], Titan Extruder [bowden]). I am using the stock steppers, which are similarly rated as the motor options with the Titan, so they should be pretty strong (driving them at 90% of rated current). I am printing in simple PLA filament, with a blower fan (on a DiiiCooler for even cooling, which starts a few layers in, at slow speeds). Looking at the temperature curve, temperatures is very stable, so it is not like the fan is cooling the heater block. To test and eliminate the cause, I swapped the Titan extruder for the original extruder, and the issue persists. The printing settings are simple: 0.2mm layer height, 60mm/s (printing speed; though I still get the skipped steps when slowing it down to below 30mm/s; this printer should be capable of printing at 100mm/s or faster if I am not mistaken). A possible cause, though based on what I have read unlikely to cause this, is when I first assembled the E3Dv6, I did not add the thermal compound to the heatbreak/heatsink threads (at that Time I was simple testing to see if my mount is correct). When I took it apart again, I was unable to get the heatbreak and heatsink apart from each other to use the thermal compound (and decided that it is probably not a big deal). Will this cause the issue I am having? How can I separate the heatsink and heatbreak without damaging either? Anything else I can try?