I've noticed audio narration is "ducked" (i.e., muted) between slides. This can be problematic in cases where the narration needs to carry seamlessly across multiple slides. If you record narration, then the volume is reduced to 0 between slides, which leaves a very noticeable gap during playback. There should be an option to eliminate the audio gap for recorded audio. Any ideas?
It's not so much that the audio volume is reduced between slides, it's that each slide's narration is recorded into a separate audio file, one per slide.
You could try recording the entire narration separately as an audio file using a sound recording app (Audacity, for example), then using the trick explained here to make it run across the entire presentation: