I found that personally when using advanced audio(determined by C2 detection) it's best to set any effects on an audio tag before playing the audio.
When using C2 audio plugin I found that audio volume in Web Audio is in fact an effect like any other, but this one is called GAIN. I found that some Effects need a moment to process before they are effectivly active.
My suggestion before any of your sounds ever play(say in splash screen). Go through all your tags and set all your start volumes(even if your aren't playing them and nothing is playing). that's the best solution i can give you for fighting this. And then I wish you best of luck