Notice as the slide travels to the rear it forces the trigger bar down which disconnects the trigger. This also resets the cocking cam.
As the slide travels forward, it feeds a new round and the striker is stopped by the reset cocking cam. Releasing the trigger allows the trigger bar to move backwards and up to engage the cocking cam. If not broken, I suspect your trigger bar is not returning far enough back or high enough to engage the cocking cam properly.