I posted about the same problem here last month. (with no response to my offer to send in an offending aaf export)
http://duc.digidesign.com/showthread.php?t=264582
I had an aaf created in Avid MC4, where two out of 8 tracks slipped out of sync at a seemingly random point, about 20 minutes in, and from there to the end of the program. 23.976 timeline, the material also imported out of sync from the beginning. The same aaf imported into my MC4 brought everything in at the correct locations, without slippage. Just like headclog's post.
Slippage problems have occured since then, with two different clients, one of whom exported from Final Cut, and the timelines are all 23.976. The same problem occurred in December from an early version of FCP (that could not export volume automation). I had suspected the editor, but now I think it happened because of Pro Tools.
I have run into the exact same problems on my last two 23.976 FCP jobs, which are omf exports of course. We all know about the fact that the actual timecode positions are wrong, that is fixed by sliding the audio into sync. But, I have also found out of sync audio. The same symptoms, the audio suddenly is out of sync for no reason I can see.
My most recent omfs from two days ago exibited all of these symptoms, again. What's worse, we found numerous regions that appeared out of sync by one or two frames, but following regions were in sync again. I have no idea why or what, is the cause.
Something got broken. Any ideas Digi? How can we help you?
And while we're complaining, is there any way to get rid of those messages that tell us regions got dropped! I mean come on, at least tell us WHAT and WHERE.