When a user starts a section translation on desktop (e.g. by providing the "sourcesection" parameter in the URL like this: https://el.wikipedia.org/w/index.php?title=Special:ContentTranslation&from=en&to=el&page=Football&sourcesection=Etymology), and then tries to publishing, the publishing request always fails, leaving the user blocked from the most important functionality in Content Translation: the publishing.
This happens because a mandatory parameter is missing from the request payload: the "sectiontranslationid" parameter.
Screencast of the error in greek (el) production wiki:
