Issues With Quiz Slide Audio

Not so easy, as far as I can judge. I suspect that you are using slide audio for the slide itself, right? You cannot control slide audio, but it is the only audio that supports CC. Once that audio starts playing it will continue till the end.

The audio attached to the feedback is object audio: it starts playing when the object appears. Since this is in the first step of the Submit process, something that is built in the quiz slides, you cannot change the action done by that embedded event at all.

You have a double issue, because neither audio clip can be controlled. The Submit button cannot be timed, it is also an embedded object. Otherwise it would be possible to have the Submit button appear only after the end of the audio clip. I have a 'cheating' work flow however:

1. Create a shape that looks identical to the present Submit button but do not indicate it as a button: use Fill, Stroke and type the text Submit in it
2. Delete the label of the Submit button, change its Fill to 0% Alpha and stroke width to 0pt, so that it becomes invisible to the user
3. Move the pausing point of the Quiz slide timeline till after the audio clip
4. Move the playhead in the Timeline panel to a little bit before the pausing point
5. Move the shape that you created to that point on the timeline (CTRL-L) and have it in exact the same location as the real Submit button

Try it out. I checked both in Browser and HTML in browser