Symbol not animating when I test movie/export

I have a mouth symbol which is supposed to be lip-syncing. When I play it in the timeline, it works fine. But when I test the movie or export it, the symbol doesn't move at all and is stuck on a single frame. It's a graphic symbol, and everything that's supposed to play once or loop is set correctly. I have multiple other symbols with the exact same settings for the same purpose that work just fine, it's only a couple that don't play at all.