I have never seen it, but sometimes the “playback” mode gets out of sync even though the final movie export is correct. Also YouTube sometimes gets things out of sync.
Hack: You could try duplicating the audio track and trimming the different segments, so CH *thinks* its a series of shorter audio tracks... then hopefully it will sync up correctly at the start of each segment.
Thanks for the reply! And yeah, seems that the playback mode is just out of sync. I've found that if I pause it repeatedly rather than playing all the way through, it syncs back up.
That may be a “feature”. Live playback is an approximation so it can go full speed (final rendering is much slower). So it gets out of sync with the audio sometimes. Just pause and replay to ensure in sync, or do a media encode and watch the result (which is much slower, but will show the “true” final result).