Maybe your last image is blank and it actually is being displayed. The way the draw() loop works is that it only displays to the screen once the loop has been completed. In this case maybe think of the screen as a collage. Basically what you’re doing is layering one cutout image on top of the other and then then only displaying it after you’ve layered all the images so only the last one is visible. Does that make sense?
Could you explain what you’re trying to accomplish? That might make it easier to make suggestions.