When using staging, we should create references to content that exists on the parent Site if that content is referenced by the staging Site. However, this doesn't work properly in a Web Content Article on the parent Site references a Document on the parent Site.
This issue is not testable in the latest ee-6.2.x because a regression was committed that prevents Web Content on a parent Site from being exported. To test this issue, you need to test on a branch that does not have
Steps to Reproduce
1. Create two databases, a staging and a live database.
2. Start up Liferay on each database and log in as the admin user.
3. Link the Global Sites of the two databases to each other via remote staging.
4. On the staging Global Site, add a new Structure with a Documents and Media field.
5. Publish the staging Global Site to remote live.
6. Create a new Site named "Parent" on each database and link them via remote staging.
7. On the staging Parent Site, create a new Web Content Article using the Structure that you added in step 4. Add a Document to the Documents and Media field.
8. Publish the Parent Global Site to remote live.
9. Create a new Site named "Child" as a child of the Parent site on each database and link them via remote staging.
10. On the staging Child Site, create a new Page.
11. Add a Web Content Display portlet to the Page and configure it to display the Web Content Article that you added in step 7.
12. Publish the Page to remote live.
13. Navigate to the live Child Site and click on the "Download Documents and Media" link.
Expected Result: The document is shown successfully.
Actual Result: The link to the document is broken.