I’ll check with the latest build when I get back on my Mac, but I also just remembered there is a bootstrap class called .fixed-top you could use also.
You’ll need to set the top to 0px. to achieve the same. Also, you increased your z-index by an additional 9000. I just learned you’ll need to be careful with crazy numbers, as the z-index is relative.
I stumbled upon this old topic. (I had the same issue recently.)
Wondering, does the nav-bloc need to be of the .bloc class, or could it be changed/overridden?
(Not sure why, but adding !important all over feels somehow wrong.)