G3M / F eyes getting 'locked' on render (but look right in preview)

I've had this problem before and never found a solution.
I apply a pose to G3M (or G3F) and the pose has eyes looking one way. Everything looks right in the openGL preview, but when I render, it's as though the eyes are looking straight forward. No amount of messing with the eyes in pose dials (either directly on the eyes or through the 'eyes left-right' part of the pose controls) has any effect.
I tried searching the forums (directly and through off-site search) but couldn't find anything about it.
Does anyone know what causes this and how to fix it?
Thanks :)