I also have an issue with background fade.
If i try to disable the fade using the value 0 in the (ms) field. It does not disable the fade effect, so when changing pages it is annoying to see the image fade in again.
I have a single image set as background in the theme options, have checked that the single pages have empty fade options.
The image is being served by cloudinary and not locally.
I use X in some sites, and this is the first time i noticed this effect.