Testing the Point module, I realized that 90° and 270° rotation are swapped. According to the figure on page 340, it should be a clockwise rotation, but it is counter-clockwise as implemented.
Maybe thats because the shown mirror axis for transpose is top-left to bottom-right in the figure on p.336, but bottom-left to top-right on p.340.
I just flipped flip and reflect for the 90 and 270 degree case.