When you use multichannel analog, the player is doing the decoding. There are a few things that may be at fault here - when using the m/c analog connection, you also have to set the distances and levels in the player because the receiver generally does no processing for that input (with a digital connection the receiver's settings are used). That leaves you at the mercy of the capabilities of the player and I believe in the AH review of the 971 it said bass management was a weakness of this player.
Next, some universal players need to be configured to select the DVD-A portion of the disc rather than the DVD-V (standard DVD) portion and many are set to DVD-V by default, so you'll have to check your manual or setup menus to see if this is an option (it should be).