Text of some stories breaks outside of its container

Reported by Caren Watkins via email

"Hi Gregor, during a scan of the stories I noticed this odd rendering of a story from last Wednesday. The student did note in their critique of the tool that the copy was running "off screen" but I wasn't clear until I saw this:" [refer to attached image]

This has been noted before in stories captured earlier this year. Here are links to the stories currently exhibiting this behaviour:
https://stories.floeproject.org/storyView.html?id=2fbf9d20-2a39-11e9-98f6-71413982cc35
https://stories.floeproject.org/storyView.html?id=2931a1f0-879b-11e9-b178-a79380bdbe47

Expected: all text to remain within the width of the site viewport, rendered in "p" elements

Actual: lines occasionally appear in monospace font, rendered in "pre" and "code" elements