Yes we are having a similar issue! No solution yet.
I had the same issue and here is how I solved it:
1. Open the audio in Edit from the Presenter toolbar
2. You will find that most likely, the person recording recorded twice and that the audio appears one take after the other. Listen to both takes (they will be in succession).
3. Select the audio take you don't want and delete it.
4. Playback and voila! One person talking.
On the other hand, it's a good way to get a "crowd" effect. I think this happens when you don't hit the Save for the recording, and just begin recording again.
Have a great day!
Can you please share me the presentation as Adobe Presenter Package and also the published output
Please send it to firstname.lastname@example.org.
Also is it possible to give the scenario in which you faced the issue
We will try to see what the issue is and resolve it for you.