Hi,
Thanks for reaching out. Yes, sometimes the object does return empty. This means that the destination didn't have anything to return. In a case like this, it is indicative of either a change in segment realizations, the segments have been removed from the destination, or something is not working correctly. I recommend checking your destination setup and segment mappings. If everything looks correct, but it's still returning empty open a ticket by emailing amsupport@adobe.com.
Best,
Tacia