Google Search Console is complaining about my forum's mobile usability. The error is: "Content wider than screen".
Example page: "https://www.contour.org/ubbthreads/ubbthreads.php?ubb=postlist&Board=83&page=1"
I can recreate the behavior on Chrome for Windows. I have no issues on my own phone (Safari).
At first glance, I think the issue is when the page contains a topic that has more than 8 pages. The pagination contains a value 'white-space: nowrap' which inadvertently creates a fixed minimum width. I deleted that in diagnostic tools, and my horizontal scroll bar went away. I have not edited the code yet to confirm it against Google.