Horizontal squiggly line at top of screen

Hello,

I am authoring a DVD of a short documentary (40 minutes) with many DVD Extras. The film was shot on DV cam and edited in Final Cut Pro. Once locked, it was exported from Final Cut and put back on DV cam. The titles were done out of FCP in HD. So was the color correcting. Since then, it has been upconverted to HD and to Digibeta tapes as well as Beta SP. Most recently, we had a Digibeta master with new titles downconverted to DVcam. We then digitized that into FCP, had to add new cards to the credits at the end, and have exported using both FCP to quicktime and Compressor. Each time, once the film is loaded into our DVD SP project file and authored out to Video TS and Audio TS, we keep getting a squiggly horizontal line at the top of the film - it is outside action safe and title safe area, so will probably not be visible once played on a TV screen (the most popular way the film will be viewed) - but it is still a concern, as we are about to make 2500 copies and do not want a less than stellar product. I'm fairly new to the DVD authoring game, and I don't know what to do about this problem.

Could this line - that kind of pops and shakes and distorts the very, very top line of the screen - be caused by so much upconverting and downconverting? We have many DVD extras using the original footage and there are no problems such as this one with that virginal footage. We could use the original locked project file on FCP, but then we are sacrificing color correction and possibly titles...I was not present for this process from the beginning, meaning when the film was finished editing, so I don't know all the steps in between offhand... Really stuck here and would love some guidance on this ASAP !

Thank you,
Andrea