sf Smallscreen menu button reverts to full desktop menu when scrolling down
I can't say for sure without seeing your code, but I wonder if this is maybe because you have some Javascript that does an add/remove class or changes the structure of the menu in order to make sticky nav items take up less space when you scroll. This symptom could only be caused by Javascript detecting the scroll behaviour, and as far as I know, Superfish does not have this feature natively (though I could be wrong, I am not overly experienced with this specific module).

If this is the case, right click and inspect code, then look for things that change dynamically on scroll. Any names of classes that are added might give you a clue as to which module is causing this. It does sound like a conflict, though, and not Superfish itself. 

If that is not helpful, do you have a dev site up that we can take a look at?

Good luck!