Mechanical releases do two things: They open and they close. They’re not terribly complicated, but misadjusted releases lead to inconsistent groups.
There are two ways that a release can be adjusted incorrectly. First, the trigger can be set too light. Archers have been led to believe that a light trigger cures target panic, because you won’t be fighting a stubborn release at the moment of truth. That’s false. An overly light trigger leads to punching, which is similar to jerking a rifle’s trigger.
There are some cool shots in this video, but skip to 55-second mark to see what I'm talking about. I'm guessing you won't understand much of the commentary here (it's in Korean), but you don't really need it. The video speaks for itself.