First layer inconsistent extrusion
Does anybody know the reason of this weird extrusion that happens only at the first layer infill.
RE: First layer inconsistent extrusion
Some of your first layer is printing with the nozzle too close to the bed. You have to get it perfect. Too far and the lines dont squish together. Too close and you get a build up that the nozzle pushes in front of itself as its printing and reacts like a wave giving you those patterns.
Make sure you are using 7x7 mesh levelling not the default 3x3. This is accessible via the printers LCD menu.
Use the Jeff Jordan first layer adjustment method if you aren't already doing so. Its MUCH better than the built in one. https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/
Preheat your build plate for awhile before performing mesh levelling/prints as this will even out any issues due to thermal expansion.
The pinda probe is also thermally sensitive so Live Z height can vary with temperature (not sure if that applies to the new superPINDA though). Yes it does add a little time to a print but thats far preferable to having print issues.
You can modify your start gcode to do this automatically for you on every print as well as making sure the PINDA is at a known temperature before starting. Details on how to do that (as well as loads more useful information) is available on Bob's website here http://projects.ttlexceeded.com/3dprinting_prusaslicer_start_gcode.html
Since preheating everything on my printer I get perfect first layers every time.