i'm having the same issue
chromebox with LE7.0.2 > Sony STR-DN-850 > Sammy tv
just 2 channels are playing, in both pass through and pcm modes
in pass through mode the amp picking up the correct decoding and shows truehd, dts-hd or dts ma but still outputs only in two front's
i hope the debug can help
i test what needed, just let me know