Thanks to the fix in pdfbox-1442, I was able to get the ch14.pdf file rendered. However the colors are incorrect. On page 13, the colors black and red in the triangle are switched. (The same error is on page 1, 15 and 20 but these take forever to render). I suspect a bug in the shadingTinttransform.eval() function.
I don't think its a bug in the shading interpolation code, because then there would have been lots of visible triangles in the spheres and donuts on the other pages where its not just a single triangle.