It isn't actually a mistake. It is a transition phase of generation. It is due to how the setting iteratively build. It is also a poorly designed generative attempt. People often try to pick general settings that will work for multiple images, but it is impossible to get high detail and contrast without causing major iterative changes like this.

A better workflow involves several stages of generation for a narrow style of image. With a proper workflow, each stage works in harmony to take the image to a desired level.

An image like this is simply a person using a sawed off shotgun to open a bottle of ketchup. It has nothing to do with the AI and everything to do with the person that created the prompt.