Since it works ok when fired, this suggests that it takes some force to retract the slide.
Maybe you're just not being forceful enough when doing it by hand, to overcome whatever is causing it to be reluctant.
Might be a stiff striker spring.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”
Last edited by g.willikers; April 21, 2013 at 08:55 AM.