Quiz with Audio

I suspect you use slide audio (for reading the questions) combined with object audio (feedback).  Can you confirm please?

You cannot hide the Submit button since it is an embedded object, which means it has no ID. Moreover it has almost all the functionality of the quiz slide built in.  It is triggering the Success or Failure action after the second step of the Submit process. The first step is showing the feedback messages, no control over that action, using the Play Audio command cannot replace the object audio.

You could try this cheating on the learner: make the Submit button 'invisible' by styling the fill, stroke, and taking away the label (for most themes it is a button from the Transparent type, and that way of styling is possible). Create an image that looks like the Submit button and put it in the same location as the now invisible Submit button. Because embedded objects are always on top, the invisible real button will be on top of the image and fully enabled. But delay the timeline of the image till the slide audio is almost finished. You have to check it out.

Altnerative would be using only Play Audio commands, because it has the advantage that when a new audio clip is launched and the first one is not finished, the first one will be stopped. But that would mean replacing the default feedback messages by custom text containers, skipping first step of the Submit button that way, so that you can launch an advanced or shared action to show the feedback based on the given answer, and Play audio at the same time. You would also need to add another interactive object to pause the slide, to allow the learner to read the feedback.Will be lot more work.