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If you add restriction to pages you will sync, you have to allow Space Sync for Confluence to view/edit the pages.
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If both synced page has an updated content that is not pushed, it will be gone by pushing your page.
To resolve it, follow the instruction below.
Get the destination page edit mode.
Push the source page to the destination page.
The contents are merged in the editing destination page.
Publish the destination page.