This is another bug, which can cause issues when trying to layback audio from your audio DAW into FCP. FCP bases audio pullup/down on it’s CAPTURE settings, NOT it’s sequence settings.

What does this mean? If you are working on a TRUE 24fps project (not 24p, 23.976, or 23.98) such as animation, AND your capture settings are set to 29.97 or 23.98, then FCP will pull UP (convert the sample rate), and the file will drift out of sync.  Conversely, if you are in PAL land and your capture settings are 25 and you are working on a 29.97, or 23.98 sequence, FCP will pull DOWN the audio, and again it will drift out of sync.

Notice the redline above the sequence in the pic above? That’s a dead giveaway that FCP is sample rate converting. Use the NO RT function in the sequence menu to check. The workaround solution is the save the audio as an Audio Only Quicktime Movie at the correct frame rate, and import THAT into FCP.