With large parts you can get away with excessively high temperatures or insufficient cooling because when it prints perimeters, by the time it finishes the first one and starts the second, the first perimeter has cooled sufficiently to become solid. That's why the base of the pyramid is ok. What's happening at the sides is that when the second perimeter is printed, the first one is still molten, so it is being pushed out of place by the second one.
Solutions:
1. If using slic3r, set a low speed for "small perimeters". Slic3r has had this setting for at least 4 years, but sadly the other slicers still don't provide it.
2. Reduce extrusion temperature.
3. Increase print cooling.
4. Reduce print speed.