Confirmation bias. Simply repeating does the trick. The interesting part isn't that this error comes up. It's that it very often decides "weird" means "pornographic" and starts to generate such an image before catching itself.
Hadn't thought of that tbh. Worth a go on Liverpool especially... that's the AWS WAF one I'm currently blocked on and it is doing my head in. The challenge there is volume rather than access (~80k decisions to backfill), so even if an LLM gets through the wall I'd still need to script around it. But could be a way in for the initial cookie. Cheers for the tip and will look into it.
Heads up tho... it's behind AWS WAF with a JS challenge. Solving the challenge once works fine, but the WAF rate-limits the IP after ~10 requests and blocks for the rest of the day. So getting a session is doable, getting through 80,000 decisions is the hard bit. If you crack it I want to know! Cheers.