It appears on some browsers, that the sweet spot of responsive switching from desktop to mobile view might have some issues with text overlapping the browser page.
Here's a screenshot and comments from @abian:
With my configuration, contents slightly overflow the page when using a window of between 481 and 560 px wide. I would increase the border between mobile and desktop view from 480 px to ~550 px (or would modifycontents so that we didn't need to modify that limit).