Explain that remote entities can cause synchronization errors if remote service is down

Author: Jonathan Diehl

content/en/docs/refguide/modeling/domain-model/entities/external-entities.md

@@ -190,5 +190,6 @@ Furthermore, external entities cannot be committed. Use the [Send External Objec
 
 * The **Commit** activity does not work. Use **Send External Object** instead.
 * On pages, the [Save button](/refguide/button-widgets/) and the [Save Changes event](/refguide/on-click-event/#save-changes) do not work when the page contains widgets that update external entities. Call a microflow that persists the changes using **Send External Object** instead.
+* When synchronizing remote entities to an offline-first client while the remote service is offline, the synchronization will fail and users will see an error.
 
 For more details on consuming services and published entities, including operations that can be performed on external entities, see [Consume Registered Assets](/catalog/consume/) in the *Data Hub Guide*.