Silence at beginning of file when roundtripping FCP>STP

[cnse]

Frequently I edit videos of live music performances. A big part of this process is enhancing the sound. Recently I've noticed that when I round trip audio files between Final Cut Pro 6.0.6 and Soundtrack Pro 2.0.2, the resultant processed audio file has 2 to 4 frames of silence at the beginning. This is a problem when I have multiple audio files that make up a continuous performance. Usually my go-to processing chain for quick enhancement is something like: Channel EQ>PSP Vintage Warmer 2>Channel EQ (mostly for the RTA)>Ad Limiter.

Does anyone have any ideas about why this process creates silence at the beginning of the files?

Thank you for any thoughts on the matter.
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Addendum:
You may ask, "Why do you have file divisions in the middle of songs?" It's because often I record video directly to disk using an old Firestore, and it has a 2GB file size limit, so when shooting a long concert, the footage is divided into 2GB chunks, which invariably never happen between songs (where a few frames of silence would be less annoying)