1. I would suggest you try speeding it up in AE.
2. Have you tried unlinking the audio and rendering the video and audio separately? I doubt that would work, but it's an easy test.
3. Last, I'm no audio guru, but wondering at that speed if you have to deal with the video in PP or AE and the audio in Audition and bring them back together after the processing is done.
You must have a heckuva long clip to go to those speeds!
Hope that helps a bit,
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