24fps audio

I have created a timeline in 24fps. The theatrical release specs from the distributor I'm working with demanded 24fps rather than 23.98. The contents include lots of relatively short clips shot in 29.97, so there is lots of frame rate conversion going on in FCP. From what I can see, the results in that regard are satisfactory. I'm in the final stage of trying to resolve audio to 5.1 (needing to create separate sub-mixed tracks for channel), suddenly sync is going haywire.

When I export a true 24fps movie (ProRes 422) audio is in sync. When I export separate elements from the same time line to .aif, .wav or .mov files without video attached, the (48Khz) audio tracks are all, consistently 132 frames shorter over 91.5 minutes (which would mean its coming out about 23.976 fps). Any ideas on how to correct for this?