Hi @crrath
Welcome to the forum! 
Yea, that’s the expected behavior with SmoothScroller using position:fixed elements inside the scroll container. The Scroll Smoother will change the context of your elements – so the fixed position will not be a fixed position anymore. Using GSAP Scroll Smoother, we have to move all our fixed positioned elements outside the scroll container. Because this is not easily possible with Bricks, we’ve created an option to detect all fixed positioned elements automatically and move them outside the containers. Did you activate this option in the settings?
If needed, you could also move only certain fixed elements to outside the scroll container, adding the attribute “data-brf-fixed” to your fixed element.
Saying this, I also attach you a screenshot from the Greensock page regarding this behavior.
I hope that this works for you 