The syncing of hidden node events fails with an HTTP 404 error.

Set the environment:

• Prepare 2 eZ Publish 5.4 installations, fully updated via composer;
• Install and activate eZ Content Staging. The standard settings are sufficient to reproduce the issue;

Ref: https://doc.ez.no/eZ-Publish/User-manual/5.x/Content-Staging/Installation

Steps to reproduce:

1. Login to admin interface and go to "Content structure" tab;
2. Create a new folder, like this:

Home
	Tests (folder)

3. Click the test folder and select "Advanced->Hide / unhide";
4. Go to Setup tab / Content staging, select the event and click on 'Synchronize'. The syncing fails:

Object <object_id> to be synchronised to feed example.com: failure (HTTP error 404 (Not Found)) [Event 1]

No errors are registered in the symfony logs. The legacy error log registers this:

Failed syncing event 1, transport error code: HTTP error 404 (Not Found)

Note: Upon further investigation, it has been determined that this only happens with content that has been created prior to the installation of the eZ Content Staging extension. There are two possible scenarios that I can see: either that content only exists on one server but not the other, or it exists on both servers, and might even have the same name, content_Id and object_Id, but it has, necessarily, a different Node Remote Id. This could explain the bug reported by the customer. Content created after the extension's installation seems to be synced properly (Hide/show events and otherwise).