PETG corners bulge out

[HerrB]

After quite some years of absence from the 3d Printing hobby, I decided to buy a 3d printer again, this time for some practical reasons rather than a hobby (proto-typing, small mounts for parts etc.) I bought the ender 3 v 2 and try to print PETG with it. So far, (I think) the Printer is well calibrated:- The bed is leveled- The prints stick well to the point where I have trouble removing the prints (temporairly heating the bed to 85°c helps removing them while preheating for the next print)- E-Steps & flowrate are adjusted, Temperature for good bridging and little stringing (210-215°c) is found (up to 75° clean overhang without support) But there is one issue, that bothers me: I can't print clean corners. The corners bulge out for some reason. I printed the 20mm measurement cube. The straight surface dimensions are 20mm. The corners bulge out by up to 0.5mm. Both on x & y:At first I thougt it might be something due to temperature/shinking but when looking closely, the corners seem to be moved in a given direction:This leads me to the thinking that bed/printhead are overshooting. Although there is also some bulging out on the left side of the Y (not as much though)the tension on the belts seems good to me and the print speed in cura is set to @40mm.Any Idea what that is and how to fix it? Oh, and by the way: how do I add line breaks? They seem to disappear as soon as I post/preview although I have seen threads with proper formatted Line Breaks...