Canson Velvet - problems applying pencils!

A patreon member of mine recently found that some of her pencils appeared to be skipping on the surface of the Cason Velvet paper! As you can imagine I investigated immediately , testing all my pencils - probably over 400 from all different brands! Check out the video below to see exactly what I found!

Note - Caran D Ache did not exibit this problem (I dont have all their colours) - Gioconda also did not have this problem.