switchback screen problem

I just bought a used switchback the other day and I`m having a problem with the screen.When you open the phone the screens work,but if you open it all the way the screen goes black.It still works,you just cant see anything on the screen.If you don`t open the top all the way the screen works fine.Has anyone else had this problem ,and if so,is it fixable.It`s kind of hard to text with the phone only halfway open.