Editing a page with Collaborative Editing enabled might show an older version of that page

Issue Summary

In some cases, After clicking on the Edit button of a page, the user has the impression of editing an old version of it.
Checking the content of the current published page and the content that appears while editing it, they are different, but seems to match exactly what it was in one of the previous versions.

For example, this is the content of the latest published version of a page while on the view mode:

When clicking on the Edit button, this is the content you get while on the editing mode:

This only occurs when Collaborative Editing (CE) is enabled.
If you disable CE, and edit the same page, then you get the current content in the edit mode, such as the image below:

This only affects some pages on a very specific situation (which is described in the next session), meaning that you don't see this behavior on all pages of the Confluence instance.

This issue was confirmed in versions 6.6.3 and 6.12.1, meaning that it may affect any version with Collaborative Editing before and including 6.12.1.

How to Reproduce the Issue

1. Have a Confluence instance configured with CE enabled.
2. Create a blank space.
   • Space Name: Space A.
   • Space Key: SPACEA.
3. Create another blank space.
   • Space Name: Space 1.
   • Space Key: SPACE1.
4. In Space 1, create a blank page with title Page 1.
   
5. In Space A, create a page named Page A.
   • Add any content you like, but make sure to include a link to Page 1.
     
6. Start editing Page A, but don't publish the contents, save it for later.
   
7. For now we have the following scenario:
   • Collaborative Editing enabled.
   • Space 1 with page Page 1.
   • Space A with page Page A with a link to Page 1 as part of its contents.
   • A draft of Page A with unpublished changes.
   • If we check the CONTENT table for Page A, there are 2 records, one for the page and the other related to its draft.
     
8. Turn CE off using the Confluence UI.
9. Start editing Page A again and publish the modifications.
   • Since CE is off, it will not use the modifications that were in the shared draft.
     
10. If we check the CONTENT table for Page A, now we have 3 records.
    
11. Move Page 1 from Space 1 to any other Space, such as Space A.
    
12. If you check the storage format of Page A, the source related to the link to Page 1 has changed.
    
13. If you check the lastmoddate value of Page A's draft, it was changed.
    • Note that the lastmoddate value of the current version hasn't changed.
      
14. Turn CE on using the Confluence UI.
15. Start to edit Page A and it will use the shared draft of the old version, prior to disabling CE.
    

Expected Behavior

1. When editing a page with CE enabled, Confluence gives you a draft based on the last version of the page.
2. Move page actions doesn't update the shared draft if the lastmoddate of the shared draft is older than the published page.
   • No matter if CE is off or on, Confluence should compare the timestamp of the current page version and the draft.

Workaround

If you identify a page is using the wrong shared draft, you can discard the draft as follows:

1. Click on the Edit button of the page.
2. Add any modification to the page and click on the Close button at the bottom right of the editor.
3. In the Close the editor pop-up, select Discard all changes.
   • If you discard changes, your unpublished changes will be deleted. You can't undo this action.