Many configuration pages allow admins to configure a user name and password for external services. For example, on the admin pages of a CMS system, you might be able to configure the user name and password of a mail server.
If this is already configured, the requested HTML page will look something like
User name: [input type=“text” name=“username” value=“admin” /]
Password: [input type=“password” name=“password” value=“xxxxxxxxxxxxxxx” /]
When autofill is enabled, Bitwarden replaces these values with the for the actual login (to the CMS in above example). When Saving the config, the mail user name/password is overwritten, and will no longer work.
A simple workaround for this would be to not autofill a password field that has a non-empty value.