the first curtain stops in the frame-
1. there is not enough force at a spring-to pull a sleeve of the first curtain.
2. the braid or edge of a curtain for something is lifted up-to examine attentively, perhaps, to move away a little a light-proof a frame.
3. somewhere a piece of film has fallen and prevents the curtain from reaching the edge - to study.
4. pay attention to the brake at the bottom, it should slow down the curtain a little, and not stop the movement-there you can bend the tongue a little.
And many other problems...