Odd, mine only has a problem when its too tight then I get grinding and slipping ( crazy huh when its tighter its worse lol ). I think i have maybe one turn from full loose. I had the same symptoms as you but with ninja flex. extruded in mid air fine. but during a print would stop..motor spin but would grind. Ninja flex was the pickiest with mine once i loosened that up..I havn't messed with it and since and haven't had any feed problems. I have not tried ABS.. I have tried PLA, PETG, PLA/PHA, and Ninja Flex. I just did 10+ hours worth of PLA/PHA prints with it the last two days with no problems. I think there is a e3d forum, maybe check there too since only a couple of us here are using them.