It's driving me nuts how sensitive the smile behavior is. It's not in the visemes, I think it's just in the face behavior. I try everything, I'm frowning harder than I've ever frowned and it just pops a smile at random constantly. Ok not constantly but too much.
Yeah - I noticed when I haven’t shaved the software reads my beard as a 'smile' or 'surprised' mouth-shape. Certainly can be a frustration. But you can always go into your mouths and untag the 'smile' or delete the 'smile' artwork and use a triggered version as Eric suggested.