A colleague used an app's "generate secure password" feature to change their ISP's web portal login - which then also became the WAN router's password - which they didn't realise. It was about a week before the router dropped its connection and needed to re-authenticate - and that's when I was called in to investigate the loss of connectivity - which Windows 10 very unhelpfully reported as the network cable disconnec…
Many, many websites will happily accept passwords of $X characters and then hash only $(X-Y) characters on registration, but try to hash all $X characters on login, so of course the hashes don’t match. And at no point do they tell you the maximum number of characters.
Fun fact: it's actually really easy to submit a string with a space on the end when entered via a PS4 controller.