I’m leaning towards a DLNA problem also. The disc I burned is playing correctly! I still erred on the side of caution and chose a core audio format (DD instead of DD Plus) but I may go with a TrueHD track next time.
It does sound as if the DLNA route is causing the issue - fwiw I’ve had strange aspect ratio issues with some versions of Plex at various times. I’d be very surprised if a disc burn didn’t work properly.