We have a content app for an EE-customer in which content is filled out for multiple languages. However, only the fallback language is required as some content should only be available in that language. If you enter no content for a language and then try to access the content in that language, the content of the fallback language is automatically substituted.

Due to the changes in MGNLUI-3491, switching the language validates the dialog form. This means that if you switch from the fallback-language to another language with empty content, you either need to fill in the content or cancel the dialog (=> losing the filled-in content in other languages). Saving the dialog or switching the language will fail, as there are empty required fields, meaning validation fails. In particular, you cannot go back to the fallback-language, even though all content was entered correctly there.

Due to this, one miss click can mean that the user loses all the content he entered.

In MGNLUI-3491, the situation is described more in-depth by this comment. As the comment explains, a detection of empty forms would be one way to resolve this issue.