Set the Video Output for all your HDMI sources to "Native" (see page 35) then the 975 will act as a switch. I don't know if this will fix your 3D problem but its a good place to start.
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975/7075/SMS-1
Aperion Verus Grand Towers & Bookshelves, Verus Forte Center, Infinity Surrounds, Ultra-X12
Oppo BDP-203, XBOX360, Xbox One
LG 65" OLED
RR2150 w/Klipsch SCR-2