What's this defect (ABS)?

[endstop]

Hi,
I'm just about to print an AntHead for my 2.4 StealthChanger (on another printer) and ran into an odd defect. Maybe cosmetic but more often than not, "cosmetic" is just the tip of an iceberg begging for discovery, the hard way.
The picture shows 100x10x10 mm calibration boxes (0.4 mm nozzle, 0.2 mm layer height, 15 % infill, Gyroid, Note: only 2 perimeters which may be more sensitive than a thick-walled stock preset).
The filament is ABS (3D Jake) printed at 260 degrees (top of the range).

The defect in question shows at the stick in front. It is rotated 90 degrees in X axis so the picture's horizontal surface is a vertical wall in print. Full of little ... lacking a better word, "irregularities".
If it were a systematic problem, like interaction with the infill, I'd expect to see a pattern but this seems fairly random.

Below, an example how it's been sliced.
For the record, it's a Prusa Core One generally beaten into submission (their forum seems to crash every 2nd time I post but that's another topic).

Cal sticks in the background are other materials (the green one the same ABS brand - fewer defects but not totally clean).

The material is supposedly dry (broke the vacuum of my own bag after drying) but please correct me

 

[5twenty]

I get this on thinner walls, and 2 perimeters is pretty thin in my experience. But...I'd orient that in the slicer with the thinner part get the infill bits like you are seeing. And the randomness, is just that; random. Most times on my irregularities, it is the entire infill I see coming through quite clearly, and very prominent on lighter colored pigments, or reds. Different filaments would behave differently as well. Some would show it, some wouldn't.

Other than my advice of: reorient the object in the slicer, you can try 3 walls, but I usually print all my ABS for function so I use at least 4. Also, a tighter...not by much...infill may help. The filament may not be getting cooled quick enough on those spans, at least for some parts.