This is a common mistake when it comes to cloud synchronization with an equally simple fix. When you compare a set of items A on the user device against a set of items B on the cloud you should FIRST check (either through file name, hash or creation/modification timestamp) that:

- An item in A is not present in B before uploading it to B. - An item in A is present in B and has changed on A before updating it on B. - An item in A is present in B and has changed on B before updating it on A. - An item in B was present on A but it's no longer there before deleting it from B. - An item in A was present on B but it's no longer there before deleting it from A.

Seriously, this is the ABC of cloud sync. Many free products also got it right. There's no excuse for the engineers at Adobe not to get it right in their overpriced products.