Issues with QueuedMongoObserver

[thequilo]

Entries might appear multiple times when the save operation of the MongoObserver fails. The local collection gets updated, but the changes don't get pushed to the server first. When the QueuedMognoObserver retries to push the changes to the server, the entry is appended again and again until the save operation succeeds.

As far as I can see, this can happen for the artifacts and resources.