When working on projects that use dual-system sound i.e. audio recorded separately from the camera, Final Cut Pro can bring up some frustrating issues when trying to reconnect the audio media files. An error message like this is displayed:
Check that the default sequence preset is set to the one that was set when the files were originally imported. In this case it was set to a 24p setting which uses a frame rate of 23.98. To set the default sequence preset, choose Final Cut Pro, Audio/Video Settings… and choose the “Apple ProRes 422 1920×1080 24p 48 kHz” option in the Sequence Preset dropdown box.
The reason why this bug/feature occurs is that Final Cut Pro assigns a frame rate to WAV audio files on import (which is set by the default sequence preset), so if the default is changed when attempting to reconnect media files then the sequence frame rates might be different, and the media won’t match.