First, if your player is decoding the lossless track, then PCM is the best possible audio. It doesn't matter whether the player or the receiver does the decoding. The resulting PCM is the same either way.
As to why your player is doing the decoding rather than sending DTS-HD Master Audio to your AVR for decoding, we'll need to know the player's audio output settings. This is almost certainly a player setting issue. Also, are you getting multichannel PCM or just stereo?
As to why your player is doing the decoding rather than sending DTS-HD Master Audio to your AVR for decoding, we'll need to know the player's audio output settings. This is almost certainly a player setting issue. Also, are you getting multichannel PCM or just stereo?