Stumped by corner defects in calibration cubes
I'm having an issue where there looks to be extra filament extruded in the corner of calibration cube prints. The problem seems to be worse on layers that don't contain part of the letters and are not full layers. In the prints below, the first is using default Prusa PLA settings on the .2 mm default Prusa MK3 profile in Slic3r PE (215C first layer, 210C after). The bottom 4 and top 3 layers are full layers. The problem is more evident in the layers between the full layers and the layers that contain part of the letter. The second image is a blank cube with no lettering printed with the same settings. The problem is worst on the layers between the full layers at the bottom and top (most of the print).
I tested the calibration of my extruder and it seems good (it printed 100 mm when I told it to print 100 mm). I've also tried printing with no infill and exterior perimeters first and the problem didn't go away.
The last picture is a print with no infill. The problem looks different, but is still present.
I'm running out of ideas. Thanks.
