Hi, I have just replied to another thread with a similar comment, I had massive under extrusion issues that turned out to be a combination of improper cooling on the heather assembly, as well as a dodgy throat tube. My printer would be fine if I disable retraction, but with this enabled I was getting heat creep that would cause a blockage. I could remove the blocked filament easily enough, but the next print would then do the same thing.If printing without retraction does not cause a blockage, check that the nozzle has been properly heat tightened and that the heat break is correctly set. Watching some videos on youtube about heat creep may resolve this.