True HD 7.1 causing video issues in Plex

[Randy Magnum]

I have an LG CX9 and when the audio is set to True HD 7.1, the video is mostly a grey screen with a jumbled box in the top left corner. The audio comes through fine, just the video is messed up. Randomly(I think it probably isn't) the video will begin playing normally, but only for a short time. When I select Stereo 5.1, everything starts working fine. I have read in some of the LG forums that True HD 7.1 will only correctly play through a hardline connection, but that seems odd, since Netflix will activate the Atmos functionality. I also have an older, much cheaper LG UHD tv and the movie plays just fine with True HD 7.1 selected. I have only a basic idea what is going on, so any opinions will be greatly appreciated. Thank you.