Has anyone experienced color fading on dyed hair after a keratin treatment?

I don't get it, I have been dying my hair blue black since 2009 (natural color is black/very dark brown) which should be very stable.
My hair comes out a tone lighter every time I do BKT and gets redish highlights even if I have it dyed 3 days before treatment.

Why is this happening? I am using Qod max Original

Has anyone else the same problem? Is there any ways to prevent fading?