In the Platform UI, after creating a copy of content translated into another language, this other language becomes the main/initial language. The copied content should have the same main language as the original content.
This issue reveals itself when viewing the content in the Platform UI (see screenshots).

Steps to reproduce

1. Create new eZ Platform installation.
2. In the file app/config/ezplatform.yml edit line with key languages and one language to the list, so it looks like this:

               languages: [eng-GB, pol-PL]
   

3. In the Platform UI, go to "Admin panel"/"Languages". Click "Create a new language".
4. Enter the name ("Polish") and the Language code ("pol-PL"). Click "Save".
5. Refresh Platform UI.
6. Go to "Content"/"Content structure". Create two new folders under "eZ Platform": "Folder1" and "Folder2".
7. Go to "Folder1". Create an Article there called "Test article" (using the "English (United Kingdom)" language).
8. Create a translation for the "Test article". Select "Polish" language for the new translation. Change the title for this translation to "Test article - polish".
9. Copy the "Test article" to "Folder2".
10. Notice that after the copy is created, you are presented with "Polish" translation in the view. It should be "English (United Kingdom)" translation since it is the main language for the original content. Also, if you look to the database, to the table "ezcontentobject" you will notice that the field initial_language for the copied content differs from the original content.