Sunken and rough bottom layer Most of my part is printing very well, but I have problems in the bottom layer and in layers that are the first layers, but not necessarily layer 0.

Looking at the print quality troubleshooting, I can't find a problem that fits my needs. Using the terms over there, I would describe it as "gaps in bottom layer".

Photo from part A (RPi case top piece):



Photos from part B (RPi case bottom):

There is a really ugly screwhole (sorry for the blurry picture):



But in the same part, there's an almost perfect much better screwhole:



For the location on the print bed, it's here (both parts):



I have seen the question First bottom layer has gaps, where the OP has already tried a lot.

My thoughts so far:


I don't want to generally lower the Z height, since it prints fine over a large area with a really flat and smooth surface.
I'm not sure I should change the temperature settings. I use the i3 MK3 printer and I use Prusa PLA filament with Slic3r Prusa PLA filament settings.
I don't understand many of the extrusion width / extrusion multiplier options of that question.
I thought I might have had a fingerprint on the print plate. I typically avoid that by wearing gloves and cleaning the print bed with alcohol every fifth print or so. However, I didn't clean before any of the two parts. (I cleaned now)


Given the description and the pictures, can you name the problem and suggest the most likely solution?

Printer and filament details:


Prusa i3 MK3
Prusa PLA filament 1.75 mm, pearl blue
0.20 mm SPEED setting
20% infill
5mm Brim
215°C first layer, 210°C other layers
60°C bed temperature
Prusa PLA default filament settings


I use a Prusa spring steel print bed. No special adhesion, tape or anything. Closest I could find in the shop is smooth PEI, but mine looks more golden.
I know you said you don't want to change the Z height, but it does look like you're printing a bit too far from the plate. I would recommend adjusting your Z-offset if you can, or adjusting the limit switch (or whatever your Z-homing mechanism is)