Why would audio snap mistake transients ?

I have a song in the box that I transferred from tape. I have lined up the grid to the drums. They really were not out much since I set the DAW at the original click track tempo that the drummer played to (in 1983 no less) and locked the whole system via my Microlynx. But here's the deal.
 
The drums consist of a Kick track, snare / hats track and a  pair of Senn 441 tracks that were used on the toms/overheads.
 
Even though the drum track is excellent, while really fine tuning what I have by enabling audio snap, I have observed that one of the tom/overhead tracks transients are consistently off by a few ticks. Sometimes by 15 - sometimes as much as 30. Sometimes even negative ticks. How is it possible that the other 3 track transients line up prefectly with no apparent phase smear or timing inacuracies, yet the one track is off ? It was a studio recording fwiw.
 
Any thoughts ?

That is a good thought. I will also go back to the studio tape and see what tracks were adjacent to the offending track.