I tried last night using an Anker Soundcore BT speaker, another cheap chinese no name brand one, and my Poly Voyager 2 headsets, and with all 3 the result was the same. When using BuzzTV 6, things were all slightly out of sync.
Watching same programs/streams On BuzzTV 5 (on the P6), everything was perfectly in sync.
Also Tested on some VOD, and using the internal player of BuzzTV 6, movies were slightly out of sync also, but using external player (I used MX Player), everything was in sync.
I will try to test a few more BT devices on the weekend.