I've had this problem before with passthrough of DD surround audio on my Bravia Android TV, after a recent update no DD audio of any kind can passthrough to my speakers (via optical). Last time this happened was about 2 years ago and was fixed in a subsequent update after flagging on this message board - https://emby.media/community/index.php?/topic/36851-dolby-d-51-no-longer-passes-through-on-latest-update1222g/
Both my QNAP server and AndriodTV app are up to date. Has anyone else been ha