I had a look at the project and this looks like a rounding error.
From the first video, the audio is equal length, o, the second one (Public) the audio is 1 frame longer.
But, the audio is exactly 10 seconds, while the video is one frame shorter than 10 seconds.
So it looks like it is a rounding error in video and/or audio.
Since there is no BITC, and since it is a mp4 encoding, it is impossible to know where the problem comes from.
Fredo