[cruse]

While testing I discovered another thing: If I rewind and ffwd a couple of times the missed: counter stops incerementing. I can see this in CodecInfo ("o" key). When the missed counter stops the a/v value stabilizes some, and does not fluctuate as wildly, and as a result the lip sync is more consistent. a/v value is not as stable as in 50Hz, but it is an improvement.

Also, as many others have said in this thread, if I disable vsync, lip-sync is perfect, but ofcourse not a real solution due to visible tearing.

You can achieve consistent lipsync and get rid of fluctuation (not the delay itself) by disabling the "Sync playback to display" option. You'll then have to "suffer" through 3-5 dropped video frames per hour depending on your hardware, as kindly pointed out by robl45.

The closer the GPU Hz/fps is to 23.976, the longer the interval between dropped frames. There are threads at AV/HIFI forums on how none of the GPU vendors deliver exact 23.976 (which essentially is 24p) but also reports on intervals of up to 2 hours with certain custom timings. Sadly there's no one for all solution since there are bazillions of hardware combo possibilities.