I recently started to have issue with the extruder stripping the filament instead of pushing it through the hot end. At first I thought it might be the hobbed bolt I got from Ultimachine a year ago. I swapped it out with my hyena from arcol. After about a day, the problem was back. Which pointed to the hotend itself instead of the hobbed bolt. Not something I wanted to hear, as that is MUCH more expensive to fix. As luck would have it I finally got my Arcol V4 in, and decided to give it a test drive in the old system.  It was compatible with the Mendel Prusa v2 with no modifications.  It appeared to extruder well, but since my bed isn’t level now the print had some minor issues/imperfections in it. I was printing with PLA, which is giving me problem, and it didn’t want to stick to itself. I will check the temp with my infrared thermometer tonight to make sure the thermistor table is accurate. I read 93k ohms across the thermistor before I wired it up, and my other was at 100k.  After a brief discussion with Laszlo Krekacs (creator of the arcol), I started using open “7” in the marlin firmware for the thermistor.  It seems to be reflecting more accurately the true temp of the arcol now.