It appears randomly in models, in two different printers. It's driving me nuts. I believe there is something to do with buggy retraction.
No I'm suspecting the "Force retraction between layers" feature. Will test and see.
Too much material, your extruder's pressure is raising while it fill a gap in your wall, than, when it starts a new line it releases the pressurized material causing this thicker lines. Good practice is to have a wall width multiple of your extrusion width. ex: A wall of 0,96mm for a extrusion width...