I also cannot reproduce your issue (i.e., it autofills both the username and password for me without problems).
Yet another work-around to try would be to define a custom linked field (linked to your Password), with the custom field label set to passwordinput. Perhaps this shakes something loose for you.
Other than that, I would suggest disabling all browser extensions other than Bitwarden (e.g., allow Bitwarden to run in Incognito mode, but do not allow other extensions to run in Incognito), and checking whether you can now autofill the Schwab site.