Razor tool mutes clip audio?

I used the razor tool on a sequence that features two videos and two audio tracks. For some reason, this causes the audio to disappear, as if it were muted? I've never seen this happen before.

In the image below, you'll notice that I have the later half of the sequence selected. That's the part of the sequence that is now silent, whereas the earlier half, unselected, still has audio that plays. I haven't changed the audio levels at all, does anyone know what's going on?