In your algorithm you use 2.48GHz frequency, however Minew also publish two additional frequencies - 2.402 GHz, 2.426 GHz. I've plugged them into your algorithm with improving wavelength calculations(lambda = c / f, where c is speed of light and f is frequency) and got three different angles. Results are presented in histogram below.

As can be seen in the plot different frequencies result in very different angles.
Do you know what's causing this?
Thanks