It could be a problem with stabilization, yes. I'm not exactly an expert on control in dreams to be honest When you have lack of vision (or partial lack of vision), I think it's best to focus on attaining sight rather than opening the eyes. In a dream it is possible to close your eyes a thousand times and recreate vision without opening them, this can also be used for teleportation (if you have sufficient dream control ofcourse). As for not being able to talk, I'm not sure. Perhaps it is enough to realize that your thoughts can be used as a way of communicating in dreams rather than talking (it is all in your head, so what is the difference really?). While thinking that don't focus too much on the face that it is in your head thought, just on the fact that thoughts can be used as speech in dreams, otherwise you might wake up.