Thank you everyone for testing the devel build. In 2016-10-18 build removed hardware demux patch and added a change to allow playing very high bitrate videos.
Now let's try another dev build that has both: hardware demux buffering and a fix for high bitrate stuttering. I believe it also has no video/audio sync issue but I leave it for you to evaluate:
LibreELEC-S905.aarch64-7.0-devel-20161018215738-r23396-g605a453.img.gz
People with "back key" issue can also try this, I think I finally fixed it - forgive me as I'm still learning sed.