When going through (Chinese, post graduate) students' essays with them in tutorials, I will point to a sentence which is so garbled as to be meaningless. I ask the student what it means and they explain it to me very well. They use a different structure and lexis in the explanation. "Write it like that, then", I tell them. This happens with the majority of my students. None of them can explain why there written sentence differs so much from the spoken one.
What's all that about, then?