What has been definitely identified on the Cinefacts.de forum are the changes in the audio mix, as this has been reduced dynamically compared to the theatrical experience.
According to information there (http://cinefacts-forum.kino.de/243067-star-wars-das-erwachen-der-macht-26.html#post8393023), the center channel of the BluRay has been “brickwall-limited” (i.e. dynamically compressed), therefore lacking pressure.