Extruder issue?  

Extruder issue?

I've had my MINI+ for a little over a week now, and am making good progress in understanding it.
Have managed to get the first layer adhesion sorted out, have printed with a few different PLA's and one PETG, with reasonable results.

There is a strange issue though, with the extruder clicking, and causing banding on prints. It's not happening consistently across different prints, but I've had it happen in the same place on the same twice today.

I am printing the large handle from https://www.thingiverse.com/thing:4619895 . Both times it got to about 12.5mm high and then the extruder started clicking.

They are both printed laying flat (on the side that's on the right of the photo). The second came out a shade different in height (on the z) with the first at 17.5mm and the second at 19.3mm. I have one other print that has a similar line (though much less of an issue) at about the same height, but lots that don't.

On the second attempt as soon as it started clicking I checked the gate, and noticed there was a bit of material in there, so I cleaned it out (without stopping the print), and repositioned the filament feed tube and sensor. the noise stopped and things continued fine for the rest of the print.

I've readjusted the extruder idler, to see if that makes a difference (have test printed something very small and it seems to be feeding ok) I'll try another print of the handles now.

When I built the kit, I got to the step where I needed to turn the Z axis threaded rod by hand and I couldn't, I had to loosen the screws on the nut to be able to do that. I was able to retighten them a bit, but only very softly, as if I tighten them too much the stepper can't raise the Z axis. Am I on the right track with this being an extruder problem, or is it possible that I've done something wrong in the Z axis build?