Keychain can't handle multiple accounts on the same website.
I have two different accounts on one website. Before I updated my Mac this was never a problem, Keychain always gave me the option to choose which account/password I wanted. Now it only shows me one account. When I try to access my other account, I have create a new password, but Keychain automatically saves that password to the first account, not the second one!! This is really screwed up and is causing me a lot of problems!
I'm currently on a Mac Studio M2 Ultra running Sonoma, with Safari 17.2.1
Previously I was on an iMac with Mojave and Safari 12, I think.
iMac 27″, macOS 10.14