I always had problem playing back large movies (10GB+) from remote NAS (site to site vpn tunnel). If the movie is copied to my local nas everything is fine.
I know what you are thinking to slow internetspeed. But I can play the same movies and alot larger movies on the pc sitting on the same LAN.
I have the same issues on 3 coreelec boxes one Odriod N2 and two S912 all of them are connected with cable.
Anybody have any ideas or the same issues ?