Has anyone opened a Stan Perfex thumb release aid?

I opened, mine to clean it. When I saw inside there wasn't much in there that came as a surprise, but when I put it all back together, the jaw did not lock when I set it to shoot. (It was nothing to do with the set up.) I took it apart again and worked the mechanism, as it can be set up all in one half of the body.
There are three parts inside and the jaw. The lever that holds the jaw in the set position is free to move on a pivot. Once the setting lever is activated, that lever should be...

Has anyone opened a Stan Perfex thumb release aid?