It is supposed to stay foreword with the cylinder even slightly open.
At the same time, it should also lock the trigger & hammer from moving to preclude any possibility of the gun firing with the cylinder unlocked.
From what I can see in the photo's the deep scaling & pitting all over the cylinder, and left-front of the frame above the trigger guard, look more like scaling / pitting from a house fire then from rust damage.
If it has been fire damaged,
the frame & cylinder heat treatment have been destroyed, and the gun is unsafe to fire with any .357 Magnum ammo.
If the cylinder lock is not working properly and hanging up, it is unsafe to fire, period!
If I were you, I would take it back and get my money back.
There are much nicer 19's around, that still work right, for the same money you paid for that one.
rcmodel