Ah, my website nemesis: poor validation and input processing.
Just entered my valid phone number to be told, in red, that my phone number was not valid. Was it the use of an international prefix? No. Was it that I used spaces in my phone number? Yes!
Forget NP completeness, AI fairness, etc., if we look at software as it is built, space removal has a claim to be one of the biggest challenges in modern software development 🙃