I had a mini dv tape digitized by Southtree which came back and mP4. I created a Premiere Project and started editing sequences. The full hour long tape plays fine but when I'm editing sequences everything from the first half of the tape works fine but the clips created from second half are out of sync.
It is constant. The dv tape is an hour long but the difficulty happens when I'm slightly more than halfway through the original tape. I have several other tapes from the same batch and they also go out of sync about halfway through. They are in sync when I'm simply playing the entire tape in my media player but ONLY when I have it in Premiere and am trying to create sequences past the halfway point.
That's an issue where the sync wasn't setup correctly to begin with, typically. The audio and video are very slightly different in "speed".
The best 'fix' I've seen for this is to go to the end of the sequence, set your timecode showing to Audio units, unlink the video & audio, then adjust audio speed track either slowing it (to 'extend' it's played time) or speeding it (to 'shrink' its played time).
The goal is to match that to the video track. For those situations where both are constant but not identical, this works to fix that. After finishing, then 'link' the video & audio tracks again.