copy and transcode response fails: "Found unknown audio codec in source "

I have a watcher that triggers a copy response that transcode's to ProRes 422 and creates an asset in FCS. It works very well most of the time except when it fails with this error: "Found unknown audio codec in source."

The source it fails on is MPEG-2 and the audio track is mp2 16-bit/48KHz stereo. Which is exactly the same as other clips that work just fine. Compressor handles the source clips just fine and I can't see any difference between the audio tracks using VideoSpec.

Final Cut Server is version 1.5.2 and Compressor is 3.5.3 running on OS X Server 10.5.8.

Here is partial audio output from VideoSpec for the source clip that fails:

Audio Track(s) Parameters
- Format: Mpeg-1 layer 2 (mp2)
- Size: 700 KiB (6%)
- FourCC: 0x50
- Number(s) and language(s): 192 (0xC0): Undefined
- Details: -
- Profile: Layer 2
- Bitrate: 256 Kbps
- Bitrate mode: Constant
- Resolution: 16 bits
- Rate: 48.0 KHz
- Channel(s): 2 (stereo)
- Position: Undefined
- Encoding Library: Undefined
- Additional Parameters: Not available

A search of the forum doesn't turn up any results, but I figured I would ask in hopes that someone else has experienced this issue. Any help is greatly appreciated.

Lukas