Duplicated content in pages after running Synchrony Hard Data Removal

Issue summary

With Collaborative Editing On and Synchrony Hard Data Removal Enabled in the Scheduled Jobs, the editor sometimes will randomly repeat the content and causing the content to be duplicated after saving the page.

Steps to replicate the issue

Creating a two pages

1. Create a page with title Page 1.
2. Create a child page with title Page 2. This page must contain some text.
3. Save Page 2

Removing Synchrony Data (Hard)

1. Go to http://<base url>/admin/scheduledjobs/viewscheduledjobs.action
2. Find on the page Synchrony Data Removal (Hard)
3. Click Run button to trigger the Hard Data Removal job.

Reproduce the bug

1. Return to the Page 1 created earlier
2. (the next step need to be done very quickly)
3. On the left side, in the Page Tree, click Page 2 link, and press E keyboard shortcut repeatedly at the same time until the page opens for editing. This steps to trigger the editor to load slowly.

Expected behavior

Exact content loaded in the Editor.

Actual behavior

Page load for editing, and after a while (few seconds/milliseconds) a duplicate content (text) appears.

Notes

Issue happen randomly for normal editing. Only when the editor took sometime (few seconds) to load. Users who experience slow network connection while loading the editor usually hit into the issue.

Workaround

Issue does not persist after turning Collaborative Editing mode to Off and disabling Synchrony Data Removal (Hard).