Markdown on the new UI sometimes breaks lines incorrectly

On the new Bitbucket UI, sometimes the markdown breaks the text at the incorrect place.
Most of the time, the text is displayed like this, without breaking the line, which is correct:

However, sometimes it breaks the text in the middle of the page, like this

I don't have a specific scenario to reproduce this (this seems to be quite intermittent), but I can assure that those two files I compared above are identical.