How to scan 'subfolders' on a NAS?

I have a NAS on my network and would like to scan all files from my PC. When I start Avast (free edition), setup a custom scan, browse and select the NAS and the folders, it finds the network device and share name just fine. When I start the scan, it scans only the root, then stops. I see no option to force scanning of subdirectories.

Thoughts?

I’m using the latest version of Avast Free Antivirus.

If you enable creation of the report file for the particular scan and let everything, even OK files and all errors, be included - what does the report show after you run the scan?
What if you enter a path to a particular file on that share (instead of the whole share) - what does the report show then?