Just want to share my newbie experience not sure if this is related to your problem,
I was having problem playing some of 3D mkv movies SBS in fullscreen when playing it directly to samsung PS51F4900, even i try to zoom it wont worked. Now i got the R6S pro and everything is solved, i can now fit the pictures on the entire screen.
Maybe it would be helpfull too if you specify the specific movie you are trying to play or even include the TV types as well, or maybe some masters here can chip in.