Compressor mpeg2 and ac3 sync issue

Wondering if anyone has seen this:
Export native resolution QT
Open in Compressor
Use "Best quality, 90 minutes" preset for DVD
Import in to DVDSP, author menus etc
Burn SD DVD.

I've done that twice this week for two slightly different versions of the same show.
First time no problem.
Second time, I get emails back about sync being off. I check the Native ProRes QT, it's fine all the way through. Open DVDSP to look at project and starting around the 40 minute mark sync is drifting out. By the time the last segment rolls around sync is off by maybe five frames. The ac3 file is 8 frames longer in the DVDSP timeline than the mpeg2. Tried recompressing with different settings, no better result.

Any ideas?
After getting used to delivering chaptered H264s for rough cut notes for my last project I really hate going back to DVDs.

DETAILS
70 minute show, Rough cut stage. RED originated, converted to ProRes for offline, 1920x1080, 23.976fps. FCS2

ak
Sleeplings, AWAKE!

Nope, sure haven't had that problem, but I can't remember ever using that workflow for a project as long as yours. I think the longest I've done was around 40 minutes.

Not to be that guy who asks the totally useless question, but is the audio in your Quicktime (the one you sent to Compressor) 48 KHz?

I have checked the Original quicktime and, for the sake of overkill, gone back to the FCP project. Everything is ProResHQ 1920x1080@23.976/16bit 48Khz right down the line. I did all the RED downconverts myself.

My workaround is going to have to be compressing the mpeg2/ac3 by acts. As we progress into network approval cycles and fine cuts for creative principals spread out over three provinces this is a pain I could do without. Looking forward to the Quantel Pablo finish though.

ak
Sleeplings, AWAKE!

Yeah, that's a good workaround. You can drop all the MPEG-2 files into DVD Studio Pro and arrange them as chapters, so they play seamlessly.

Well I did that but every Mpeg2/ac3 had the same but smaller duration differential so when you string them together on one track they drift out of sync. I just made each chapter a separate track and had them play sequentially. PITA but it works and stays in sync.

All I need to do now is figure out why I am getting differing durations and sync drift from an otherwise synced QT. arghh!

ak
Sleeplings, AWAKE!

I am just remembering now that I installed that most recent prokit update between the last rough cut DVD delivery and this one. Wonder if that has anything to do with it? Ugh!

ak
Sleeplings, AWAKE!