My line widths are all 0.4mm and I'm printing on the original Creality CR10 with 0.4mm nozzle, I changed the acceleration because I thought it was too much, I decreased it in hopes it would spend longer on the corners as it's under-extruding on the corners themselves too, and just after. I tried changing it back to original speed just now and it didn't make a difference.
"retract at layer change" is unticked.
I'll look into calibrating the extruder
Thanks