Sometimes using autofill in subdomains of my team, fill with wrong login/pass !
In this example dev.edu.pt fills sometimes with wrong login of site.edu.pt, and the most times with the correct login
I’m using option host for urls !
Hard to say what could be going on, but I would scrutinize your login pages for any cross-site login forms that would mess up your URI matching. This is not uncommon - you open a URL to one site but the login form that appears is actually being generated on a different server.
Its be rare to happens !
I had scrutinizer login URLs, and dont has cross-site URLs, only have the somme domain (ex: edu.pt)