That kind of issue on the encoder OR player side would've been easily caught in testing, including through automated tests, so as crazygringo says, it's most likely your OS/hardware.
that's pretty good, bip bop, those line up spot on. I wonder if its quality/resolution dependent. That test video is 360 max. Whatever I'm perceiving if I'm actually seeing something is in the ms range, it's not obvious it's like right on the border if I trust my senses.
If you need to troubleshoot sync issues, this is a helpful tool: https://www.youtube.com/watch?v=HD4emXqHCsE