On the source server:

1. Create a new content object.
2. Delete the newly created content object.
3. Try to synchronize the feed.

The following errors are displayed (see screenshot):

Event synchronisation action results :
Object 146 to be synchronised to feed target: failure (Can not serialize object to be sent) [Event 5]
Object 146 to be synchronised to feed target: failure (HTTP error 404 (Not Found)) [Event 6]

Note: this is a known issue/limitation of ezcontentstaging.