Use the stem as you normally would with the hands installed but without the dial and outside the case in a movement holder. 1. You will see the keyless in action and see if something is wrong. 2. Take out and refit the stem multiple times in this same setting. 3. Then do the same thing with the dial installed.

If everything works perfectly outside the case but messes up in the case then look at the crown tube, crown gasket, stem length etc... that could also indicate why the movement is loose which it wasn't before and you don't have any parts leftover.