I have not experienced any difficulty in syncing ADATs. If you are punching into record in the middle of a song, they can take a few seconds to sync up. So while I was overdubbing a Pedal Steel part
the Engineer just had to start the tapes rolling a few measures before the punch.
Once they lock up, they stay in perfect sync while playing and recording.
This was a few years ago, and I think the new machines are even better!
Dom Franco