I believe there is a network traffic bottleneck somewhere. I understand your switch operates on Gigabit mode, however, if this is indeed the Ethernet port of your unit…
…Then it uses a 10/100 (Megabit) Ethernet port, which would create a bottleneck for LAN 3D playback.
The My Cloud doesn’t know the difference when your projecter is in 2D versus 3D – it doesn’t even know what the file is. The issue must be with your projector – though I’d be hard pressed to understand what that is…
Your right its just a data file as far as the NAS goes.
I do think this is a possibilty that the projector could be an issue.
The only thing that makes me hesitant is the same films from a WD elemts play (via HDMI directly to AV amp) work fine.
Along with bluray discs themselves are ok.
What I can do thinking about it is transfer a 3D film onto a USB stick and plug that into bluray player so the network is bypassed and see what happens.
The USB stick with the 3D film that plays fine if plugged into the bluray player when 3D is enabled on my projector.
Tuns out the NAS can play attached USB devices as well, so I plugged the USB stick into the back of NAS and the same problem occurs when 3D is enabled. White flashing on playback when 3D enabled.
So using the NAS and 3D does not work in my settup.