There was indeed a small portion wider just at the tip, that looked like the photo you posted here, a bit shorter in length. Unfortunately, I threw it so I can't measure anything, I just lanched a print of the repaired file, and will keep you posted. There also was a little string that came with the filament when I unloaded it.

Additionnaly, I don't get jams, but sometimes clicking in the extruder, if it helps. (I tried to clean then grease the gears, cut a bit the PTFE tube that was overshooting a bit, it still clicks at times).

Thanks a lot!

A clicking noise is never a good sign and made lead to underextrusion soon or later. I would try to eliminate it by either reducing the print speed or watching your ambient temperature. I may have different causes, but I would investigate because it can cause serious problems further down the road.

Additionnaly, I don't get jams, but sometimes clicking in the extruder, if it helps. (I tried to clean then grease the gears, cut a bit the PTFE tube that was overshooting a bit, it still clicks at times).

Thanks a lot!

The filament sounds like it was chewed by the extruder gears. Normal with jams.  The very tip is of interest though: especially any stubs that formed.

The curves exceed the printers ability to form layers ... that's where your problems start.  Those holes should be chamfered for printing.

That makes sense, I put a chamfer, it will be better now.

The part also has errors. Hard to say what they are, but they may impact printing.

That's weird, its quite a simple part, idk what caused them. I tried to change a few things on SolidWorks, but the errors were still here. So I repaired the stl online, no more errors. Here it is, in case that helps.

And last: if you unload filament after it stops printing, what does the tip look like?

Good question, turns out I noticed it was unusually damaged: it was flattened and brittle around 8cm from the tip, which I don't remember happened before.

Thank you very much and have a good day!

The part also has errors. Hard to say what they are, but they may impact printing.

And last: if you unload filament after it stops printing, what does the tip look like?

I am having an issue with my MK3S (Grey Prusa PLA, .25 nozzle, standard temps, Cura slicer configured for Prusa MK3S), although it had been working quite neatly for a few months.

When printing this object (the big flat portion on the bottom), I have a weird issue (for which I found nothing on this forum or on Google): the nozzle starts printing in the air. I have tried this piece 3 times, including once at a bigger size (with more slots, see the picture), and every time it seemed to happen roughly at the same time. I come back and find a blob of plastic on the nozzle, and the print head moving as it should but above the print.

Before the last failed try, I tried a similar design, but in smaller (with only one slot), and it worked perfectly.

Any idea/tip would be greatly appreciated.

As you can see from the picture, I have another issue, albeit less important: there are filaments in the "holes", that should be on the outline, but I gess didn't stick. If you know how to tackle this issue, I'd love to hear your solution as well.