I know this question is old, but I just ran into the same problem and wanted to post what I found out.
Has your audio player downloaded audio successfully? If src = "#" or if you gave the player the wrong path to the sound file, the line of code that you specified will throw the error you specified.
I would suggest trying the following code, where audioPlayer is the identifier of the audio element, in order to perform a simple check that the audio file is really loaded:
if (!isNaN(aud.duration)) { aud.currentTime = vid.currentTime; }
But of course, if you expect the audio to load, correct the path to the audio file
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