Not meaning to resurrect a dead thread, but I can actually confirm this happening when setting the height/width of the promo slider to 100%. In my theme I have this: https://pastebin.com/qkphbgAU. The header container is a fixed width of 800px, but even when using two images of the same size as promotion images the page scrolling occurs–with no modifications to any of the promoslider plugin code.
