How To Debug And Solve The Problem Of A Horizontal Scroll Bar On Mobile Devices
This is due to an element which creates overflow. You can quickly find which element is causing the problem by following the instructions here:
Once you’ve determined which section has overflowed, you can edit that Section’s Layout tab, and change Overflow to Hidden.
If you prefer, you can opt for a less technical way to find the section that has overflowed. Simply save the page as a template, then edit the template. Delete each section, one by one, and test on mobile after each deletion. When the problem disappears, you’ve found the problematic section.