Hi,
I have the exact same issue, however mine is sporadic. Most of the time the audio is in sync, however sometimes it goes out of sync.
I have the PHILIPS 55OLED806/12 Smart TV.
This happens sometimes in live TV. What i have noticed is if i am watching BBC1 HD channel, there is a lag, but when switching to BBC1 SD there is no lag. This seems to happen only on the HD channels from my experience.
Then when i am watching a series i have recorded. For example i am currently watching Capture, which was recorded on BBC1 HD.
I just watched Episode 2 with no lag, and then moved immediately to episode 3 and this one does have the lag.
If i try to restart it, watch it at another time, it makes no difference. The lag is there for that episode as recorded and cannot be fixed with any audio delay setting changes on the box or on the TV itself.
I do not have an external speaker connected. This is coming through the TV Speaker.
This issue does not happen on my other externally connected box for IPTV, nor does it happen on Netflix, Amazon or disney+ or any other device.
Any ideas would be very helpful.