Here's a sample - just moved a few of the expression builder sliders - maybe it's just a limitation on the smaller faces? Haven't had this happen with the adult actors.
I can get that kind of thing to happen with adults too.
I think the moral is that the expression builder sliders are good for manipulating the eyes and the mouth independently, but when you start applying several changes to the same part of the face, stuff starts getting weird.
If you can tell me exactly what sliders you moved, maybe you can convince me that one would reasonably expect something different to happen. But it may not be possible to do anything about it.