[تم الحل] Translation stuck at 99% - 1 string will not save

Background of the issue:
I am trying to translate a post on my site الرابط المخفي using WPML. I have followed the WPML Documentation and support documentation.

Symptoms:
Translation is stuck at 99% because 1 string will not save.

Questions:
Why is the translation stuck at 99%?
How can I save the string that is not saving?