Comparison Affine Coordinates and Projective Coordinates Addition in Excel
The projection coordinates you got are wrong. We can tell that because those coordinates do not correspond to a point on the curve.

We have $15 \cdot 9^{-1} \equiv 17$ and $2 \cdot 9^{-1} \equiv 13$; when we plug $x = 17$ and $y = 13$ into the original curve equation, we do not get equality, and so we know something went wrong.