I noticed a strange issue when rendering video out in Reaper.
The first time I render, the audio is out of sync, delayed a few seconds from the video. Then when I render the 2nd time, the audio is in sync.
Here is a video showing the problem:
https://youtu.be/deO7WZ2QMRM
At time 1:05 I play back the 1st render, and you can see from when the meters in Reaper start, the audio starts a few seconds later and is out of sync.
At time 2:17 I play back the 2nd render, done with the exact same settings, the audio now matches with the Reaper meters.
The same problem happens both with the wmf and ffmpeg encoder.