I have re-read the warranty as it is available online.
I have doubts whether the warranty applies here as it is related to hardware not software, and I am assuming there is no manufacturing defect as you said.
You mentioned there are other people around, have you tested any device which would behave in a desired way?
Edited to say that the topic linked by @yvmuell was very informative
@Deebbiie could you possibly try turning off the speaker when you talk? I am not sure how doable that is. Plus someone mentioned Zoom settings..