I am using a rectangle to select an area of the model I want to have 100 % infill. You can see my setting below. After several prints, I noticed the little arm was still breaking when under pressure... and sure enough my infill setting had not worked. In looking at the preview in Cura, you can clearly see it is not applying the 100 % infill as you can see set to the left... what am I missing? I have tried several infill types,(lines, hexagon...) to no avail.