I can not calculate it right now, because I have quite a complex 3-days optimization script running; but don't you find these spikes suspicious?
More I look at them, more it looks like the spikes point at correct values, while other continuous sections represent something duplicated from the reference PI data.... Can you try overlapping them, in GIMP, or in PowerPoint maybe?

BTW, I forgot to tell you that I always use second order or mixed order simulation (because I always deal either with curves, or with sharp edges providing curved field profiles).