thank you all @charlie.brooker @chris @SaeranVasanthakumar and all the others that chimed in!
We had a bug on our end!
the line:
dir_bins = np.arange(-22.5/2, 370, 22.5)
(Why 370???)
was generating bins with the following labels
dir_labels = (dir_bins[:-1] + dir_bins[1:]) / 2
print(dir_labels)
[ 0. 22.5 45. 67.5 90. 112.5 135. 157.5 180. 202.5 225. 247.5
270. 292.5 315. 337.5]
360 is missing!!!
the problem is solved with:
dir_bins = np.arange(-22.5/2, 360+22.5, 22.5)
dir_labels = (dir_bins[:-1] + dir_bins[1:]) / 2
print(dir_labels)
[ 0. 22.5 45. 67.5 90. 112.5 135. 157.5 180. 202.5 225. 247.5
270. 292.5 315. 337.5 360. ]
and this is the resulting windrose for Riyadh:
Thank you for your help! 
We’ll fix it asap in the live version