Hi jrs007, I stumpled upon your post today having the same issue. With your help I found out, that the snapshots are the troublemaker! So I took a closer lock to the options that the NAS give me , and found a way to make them unvisible to plex:
-open Snapshot Replication
- choose Music (for example)
- Settings
- Extended
- remove the check “snapshot visible”
This helped me!
btw. : excuse my poor english 
Greetings from Germany!
Jochen
