Audio Sync Issues

[BluMax]

First thing to introduce myself: I'm a digital tekkie with working with the digital platform for over 10 years.

I found DCP-O-Matic back in 2015 to produce DCP content for the multiplex I was working at.

We would receive ads on thumb drives from clients in the MP4 format and I would use this product to produce these ads with great success.
Yet, I learned that I must use the audio settings to reduce the dB output to the completed DCP file.

Later, I would create MP4 files from ripped DVD's and use this product to make DCP files for presentations ... which would work just perfectly.

Lately, I had two occasions were the MP4 file processed to DCP where the audio lagged behind the video. Yet, the original MP4 played spot on.

Original MP4 had a 24fps frame rate and the product senses the frame rate, thus the result display below the tab pane showed "same frame rate."

When I proceeded to the Job tab and the Make DCP tab, the window opened up and showed that everything looked great in order, thus, on to the creation of the DCP.

After creation, I ingested the content into the server, did the test playback, started out great, then half hour into the performance, off sync was beginning to show up.
I tried again with production and with same issues.

What happened, or did I miss a few steps. Thx for the help on this.

[BluMax]

Addendum to my topic:

I did look at the properties of the MP4 file and the audio is posted at 23.98fps . Would this cause the later sync issue?

Thx for the help on this

[carl]

If DCP-o-matic thinks a 23.976fps file is 24fps that can easily cause a loss of sync. Can you send the "metadata.xml" and "ffprobe.log" files (from inside the DCP-o-matic project folder that you made) to carl@dcpomatic.com ?