I found this behavior while translating WPSEO. It has an original string that reads so:
__( 'Replaced with the post/page author\'s \'nicename\'', 'wordpress-seo' )
It should appear thus in CSL's table and edit windows:
Replaced with the post/page author's 'nicename'
However, it appears as:
Replaced with the post/page author's 'nicename\
And as a result, the translation I added for it didn't appear in the corresponding location after generating the MO, the original string appearing untranslated.
I hope this helps!