Weird bug with lipsync or am I missing something?

I have a clip of dialog around 2 minutes long, jumping between multiple characters, and it works fine up until 65 seconds into the clip, when the lipsync freezes for all characters and they just stand there with the last syllable they said on their face. Looking in the motion editor, there are still motions listed for their faces, but none of the sliders change value when I pull the playhead after 65 seconds. Anyone know what could cause this?