The only content in the "overlay" placeholder is an empty "Container". If I have no content whatsoever, then there is not scrollbar - but as soon as I add any content then I get the scrollbar.
EDIT: this seems to have something to do with the definition of the "row" css-class (which I think comes from "bootstrap"). This has "margin-left: -15px" for example. Any way to override this when defining the overlay?
EDIT: this is for Sitecore 10.1; SXA version 11200 (from "/sitecore/system/Settings/Foundation/Experience Accelerator/Upgrade/Current")