From the manual;
[BD Audio MIX Setting]
[On]: Outputs the audio obtained by mixing the interactive and secondary audio to the primary audio.
[Off]: Outputs the primary audio only.Select this to output HD audio signals to an AV amplifier (receiver).
Double check this setting and make sure it is set to OFF.
HT TCL 55P605, Mitsubishi HC6500, Oppo UDP-203, Panasonic LX1000, Firestick 4K, ATV4K, Onkyo TX-NR787, DefTech, Klipsch, Martin Logan, SVS @ 5.2.4 Atmos
Stereo Sansui SR-4050, Dual 1219, Oppo BDP 83, Emotiva PT-100, Be One Audio MA100, Polk Monitor 10, SVS SB1000