Walking While pressing a key

hi ..... my problem is that y want an object (people) to walk while the key (up) is being pressed. it goes fine until i stop pressing that key so alice popup an error screen with animation problem... does anybody know how to solve this ??


EDIT: i uploaded an example of my problem....... when you are pressing the up key everything is fine but when you want it to stop by stop pressing the up key there comes the error please help me how to fix this