Do you use a custom save button to save the object in DataView[A]? If so, this microflow is responsible for committing this object and all objects in nested DataViews to the database. A default save button will automatically also commit the objects in all nested DataViews (if not readonly).
Before triggering a microflow, all object changes are sent to the server. As long as your server keeps running, these changes will stay in the runtime's session cache, waiting for a commit. That's why when reopening the form, it seems like the changes are committed. However, when restarting the server, these changes are gone.
By the way: be aware that the DataViewList is quite a heavy widget, and you may run into performance issues when nesting it.