I've been trying to print an object using PLA. It seems whenever there is a geometry change that results in there being a partially solid infill in the layer, the outer wall seems to end up missing in that same layer or is not adhering to the layer beneath it.

Nozzle Diameter: 0.4mm
Layer Height: 0.2mm
Bed Temp: 50 C
Nozzle Temp: 220C (The brand specified between 215-225C
Shell Thickness: 1.2mm
Infill: 20%
Top & Bottom Thickness: 1.2mm

Has anyone had this issue? What are the possible solution to getting around this.
I've been trying to add pictures that I took of the part to this post but cant seem to get it to work. The pictures are under 1 Mb each.

Figured out how to get the pictures to upload

Update: I've printed this part 3 times now. I was able to reproduce the same missing layers in the exact same spots.

Could it be retraction problems or filament slipping or extruder missing steps?

Depending on slicer settings the perimeter is printed first, then infill, then retraction, z moves, then petimeters again. The retraction could loosd steps and stop extruding until infill is reached, making it appear the outer shell isn't printed. Check if the printer is going through the motions of printing the missing walls/perimeters.

Did you have a look at the g code? Did you observe or took a video when this happens, found anything of note? Try to isolate the problem and have a smaller print in a similar way so it's faster to try things and test it.

You could try reducing retraction velicity and acceleration (check jerk too) to see if that make any difference.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]