Syncing issue on NAS

On my Synology NAS (vault), it still has 13,383 files to receive (download). It has been like that more than 24 hours with no progress, is there anything I can do at OS level to speed it up? Thanks.

The primary vault is an USB external drive attached to my Mac, this is where all source photos/videos came from. I recently added Synology NAS as a secondary vault, which is also attached to my Mac.

Note: Mylio is running on my Mac continuously.