Q: Soundtrack pro off sync exporting back to FCP 7

Hello,

I'm sending my sequence to soundtrack pro from final cut pro 7 timeline to edit the sound.  When I export it back into final cut it is off sync.   It starts off fine, but gets way off towards the end of the timeline. I also tried to export the audio separately, just the audio without the video, mix in Soundtrack Pro, save as an aiff, then import back into FCP 7 and it is off sync, too. I've tried this over and over for hours and not sure what is happening, I've not had an issue with this in the past.

Thank you for your help!