Any wall under 1.50mm usually will not be filled only outlined. I've always printed at 0,20mm and 60-100% infill. However it's gotten so annoying I've considered just going back to a free slicer.
The area in question is 4mm wide 3.75mm long and a 1.35mm screw hole. using two shells per normal. Thin wall behavior set at default 10%, adjusting this does nothing. How can I get around this? If you need more settings info please let me know.
