Cannot reset password

When trying to reset a password, I have two issues:

First, the reset link in the mail doesn't include the fully qualified hostname, but only the hostpart. I can work around this by changing the email template. On the command line, "hostname" also shows only the host part, not the FQDN.

More serious is that the password reset form doesn't seem to work. I get to the reset form (user name correctly shown uneditable), but submitting it fails with "Your reset code is invalid".