Audio Sync with Intensity Pro

I've searched online and found other people have this problem, but haven't seen a solution. I'm using the Intensity Pro to capture VHS and am ending up with wildly out of sync video. I'm trying to capture 2+ hours and by 10 minutes it's already very noticeably out of sync (and gets worse as it goes). I working on a 2012 Mac Pro to a 3 TB raid in Final Cut Pro 7. I've also tried installing the card in my 2009 Mac Pro also capturing to a Raid. My disk speed test show that NTSC footage should be fine to read and write. I previously used the Decklink HD extreme on the older computer and had no problem capturing HD from SDI inputs so I can't see how disk speed would be my problem. Any advice is appreciated.