SMPTE offset for MTC

Im also noticing that there is a significant amount of drift happening in the audio of video files; even when syncing internally with no MTC. By the end of a 10 minute clip music track that I add are off by a second in the final render. if I do an offline bounce and start playback near the end, the music is in sync. This is also prevalent with automation. Simple volume automation doesn't line up with the audio in the video file. Any ideas?

Bump... Can anyone tell me if there is a smpte offset for mtc sync?

bumparoo...