When I try to change the picture in the codes in MIT App Inventor, the picture that comes with the code works at startup

I'm trying to add an explosion effect to the 'Space Invaders' game. For this I went for image replacement in ImageSprites. When one of my two spaceships was hit, it had to be replaced with an explosion patch. However, when the game is opened, the game starts with this explosion effect. how can i fix this?

You may share your work which is to be fixed.