Thanks for your comment Pip4.
I'm surprised that a reset actually helped with this issue at all, but I'm glad it did for you for a while, at least.
I wish Samsung would be less complacent and more customer-focussed. After all, each dissatisfied customer = future sales lost!
In my case, it is only the "Bluetooth" that delays the sound, I have tried it with cheap and expensive headphones both fail.
However I have bought an optical converter that plugs into the Digital Audio Out (Optical) port on my TV. This in turn has an old fasion "Headphone" sockect which I use to connect an old fasion "wireless" headphone (not bluetooth) transmitter and wireless headphones.
No lag, stupid yes but no lag.