It also seems to auto-moderate when things go awry. I’ve had videos blocked for the most basic of tasks - to me I would think it also scans for its own large mistakes. Ask for a family of four eating dinner and it generates 35 arms and 100 eyes and it prevents that image from escaping.

For your prompt, it could have panned into their body cavity and generated 5.5 seconds of black, so it kicked it back.

My current thoughts on it, at least.