Localized lesson content is overwriting or being appended to English content

We've seen two instances so far where translated/localized content has been interacting unexpectedly with English content, and we're not sure how it's happening.

1 - In today's instance, a German quiz was being displayed at this URL, instead of the original English quiz:

https://learn.wordpress.org/quiz/introduction-to-wordpress-2/

(The German version of the quiz has since been re-translated back into English, so you'll see English there now.)

The German quiz was intended to belong to this German lesson (note the de in the slug):

https://learn.wordpress.org/lesson/de-introduction-to-wordpress-2/

But somehow got connected to this English lesson:

https://learn.wordpress.org/lesson/introduction-to-wordpress-2/

Notes/potential clues

• The English course to which the lesson belongs is published, while the German one is not.
• The German quiz URL was missing a -de at the beginning of its URL – not sure if that is expected.
• The German lesson is not assigned to any course.

2 - In an earlier case, a German version of the same lesson was being displayed in the list of lessons within an English course:

In that case, perhaps the lesson was accidentally assigned to the English course?

@devmuhib009 and @rfluethi – if you both have a chance to add any details you can remember about the steps you took around this particular lesson and quiz, that might be helpful in figuring out whether there is a Sensei issue that we need to look at. Thank you so much!

Start by reviewing the linked English and German lesson and quiz URLs, then trace how localized lessons are assigned to courses and connected to quizzes. Compare the published English course with the unpublished, unassigned German lesson and reproduce the incorrect relationships if possible. Done means localized content remains associated with its own lesson and course without replacing or appearing in English content.