If the default locale for a site is changed, then content based on structures (including Document Types or Web Content Structures) will not copy the value from the default to other locales when translations are created.
Steps to reproduce:
1. Add a new site, and check the default language of the site (for example "English (United States)").
2. Go to this site, and add a new Web Content structure. (The default language of the structure is should match that of the site)
3. Add a text field into this structure.
4. Add a translation to this structure for a different language (for example "Spanish (Spain") -> Save.
5. Go to Site Settings -> Languages -> Change the default language of this site to the second language chosen in step 4 (e.g. "Spanish (Spain)").
6. Add a new web content in this site with the structure created in step 2. (The default language of the web content is the site's new default language).
7. Put some values in title, summary, and the text field.
8. Add a translation for the original default language for the site (e.g. ("English (United States)").
Expected result: The new translation starts with the default language's value copied over.
Actual result: Only title and summary are copied over. The value of the text field is not copied over to the new translation.
Not reproduced in master: d79957d12aeec180335825a3bf2466af95f3fd9b
Reproduced in 7.0.x: 2532feff903981444b2a9a673e6625bdb3b7b06a