record narration issue

When I record the narration for each slide, I may have to rerecord because something did not make sense or other reasons.  I stop the recording and start recording again.

the issue is when I preview the whole presentation, the slide where I have rerecorded seems to have kept both versions.  so they overlap each other.

When i use the audio editor I only see the last sound bites.

how can I resolve this ?  it is the second time I have recorded the narration and still I have the problem.

It is only with this one presentation that is has occured and it is frustrating as I cannot proceed with the rest of the work.

help please

Vincenzo