Hello
Footer and pre-footer (HTML blocks) does not show as intended on mobile device. This problem happens only on elementor designed pages (Ex: home).
Yes, it is a bug in the Elementor plugin and you can read a similar issue on their Github https://github.com/elementor/elementor/issues/16467
As a workaround, you need to click on the “Preview” button while editing your footer HTML block. And always keep the preview window opened whiled customizing and saving your HTML blocks with Elementor.