For starters, PP will only sync one clip per track, so if you wish to use this feature, you'll need to shoot continuously, no stopping until the event is over.
Secondly, the feature doesn't seem to work very well (at all?) when including a separate audio track in the mix, so use video clips only.
Thirdly, it is a new feature for Premiere Pro, and will likely get better over time.
I've been trying and it seems like multiple clips from a single camera just
get interpreted as more cameras and then I mix them down to the correct
track after waveform sync.
I figured out te problem. 16 clips synced and 8 did not. Those that did not sync were all from one camera which was significantly further from the audio source than the others, so its audio sounded different. I manually synced that camera and am back to editing. Feature request - more thorough audio processing!