There is no fade-in. My guess is that it has to be a sound driver issue but have had no luck in reinstalling sound drivers. Interestingly, when I export the sequence to file, the sound starts at the beginning in the produced video file as expected. Very weird.
When previewing an edited sequence, it takes about 5 seconds before the sound starts. When it does start, it is in sync. So no sync issue, just missing the first 5 seconds of sound.