Since changing the set up to use BTT370's Optical-In input from Tv, with two Pvrs connected to the Tv, we too immediately noticed that lip sync needed adjustment. This was also in spite of the delay in the Sound Menu being left at 'auto'
Are you sure the audio is behind the video? It was hard to be sure and at first it seemed odd to be adding delay in this situation, but in retrospect it must have been the lips 'moving too late' which meant that adding 'delay to the sound' was the answer.
It was reassuring to see how lip synch gradually got better as the setting was increased in stages from 10ms, so in our case this seemed to confirm that this was the right thing to do.
Unlike what you found, changing that 'Auto' setting like this, up to '90ms', (with 0ms in all the speaker settings), has cured it completely, so maybe you could have another go to make sure