I'm amazed guys!
Sync is a NON-ISSUE30 years ago, it was a constant pain and a battle - SMPTE lock ups to loads of drifty unreliable analogue gear. Now, if you have a mix of modern card recording domestic, prosumer and pro gear, then as long as they are all locked to the same frame rate you can sync your cameras at the start of a one hour recording and forget it. You can develop bad habits and they cause ZERO sync issues. Drift and sync loss is VERY VERY rare.
It doesn't matter if your camera produces a single long file, or multiple short ones. Butt them together in the editor and sync is solid.
Depending on the music, you could use clever software to do the sync, but I haven't needed that for years - plural eyes worked well, but just not needed.
The key factor is the audio waveform in your editor. It's a roadmap to getting the cameras close, and it's very obvious. with the entire recording visible, slip and slide roughly because the start time of each camera is different. Then find an event. The big tutti section, or if you remembered, you standing in view of every camera clapping, or that obvious cymbal crash. If it's prominent, then every camera's mic will have captured it. Zoom in on that in the waveform, and slip, frame by frame till they match. Remember the distant camera will be audio behind, and at the frame limit, you might be unable to get the peaks to align. I just allow the further cameras to be audio behind rather than in front. In Premiere I then trim the beginning of every camera to align. That's sync done.
Problems? I have one camera, about ten years old now that has a real fault. Randomly, maybe once every five-ten minutes, it drops a frame. I know this, so before I start editing, I run through the timeline looking for mismatched audio peaks from this camera. I cut the track and drag the timeline a frame, and it's back in sync. I usually just extend the left side to close the gap, effectively duplicating the odd frame. If one of these happens to be visible in the edit that follows, I just fix it with a one frame shift then.
Camera audio allows this to be totally foolproof. The only time I got caught out was in a large church where I managed to get one camera right at the very back, and the audio took 200ms or so to get there, and I forgot to compensate as the result was a delay on the video. The conductor spotted the batton wasn't quite right. I hadn't realised they could spot their hand actions being out of sync by such a tiny amount!
Churches, choirs and large events are not at all problems for sync. With gopros, I can have 8 streams to sync on stage, and it's never an issue.
I just finished recording a studio recording where sync was trickier. People were comping vocal and instrument tracks in two bar phrases. The video files would have between two and six attempts at each phrase. They then comped these takes into the finished product. I was a little worried about the sync, because they did the usual audition each one and move it to a new comp track, so I didn't have any information on which of the takes on the camera was the selected one. However, once I got the completed comped track, visually there were differences between each take so I'd look at the take in Premiere, and see maybe 4 waveforms, I'd have underneath the comped track, and then with a little slip and slide, the right one was fairly easy to find, and sync - and even when two looked exactly the same on the screen, even the wrong one synched. I think I can spot a couple as I'd heard the damn things over and over again, but nobody I tested them on could! For interest, this does fall down on BVs - where they use time stretch to align different takes. Not sure if you've come across this, but imagine maybe five people singing their lines, but with the way they say the wordds and the timing slightly different. Cubase, for example, lets you place them abive each other, designate one as master, and then the others get stretched and squashed to fit. Sounds great, but messes the video up no end. Luckily in the video, BVs where there are multiple voices don't seem to look wrong. You'd spot it in the lead vocal, but it's OK in the backup vocals.
Just don't get spooked by video sync - In Cubase we fiddle with teeny timing issues. In video we're locked to video frames. For me, it is a very rare thing to have to take video into Cubase to shift audio by a quarter or half a frame. I can do it, but it really doesn't matter with live recordings because audio in an orchestra/choir/on stage always has very large delays as part of the experience - 300 Metres = 1 second is quite a long time when we so often moan about 10mS latency being intollerable!!