Wrong authentication mechanism while using GSSAPI for one of the account on the same server
If you have second account from the same server, and server promote GSSAPI auth, Gajim would use default kerberos ticket for auth. So, you will get two connection to the same account. I think Gajim should not to use GSSAPI, if password is specified or check JID user match kerberos ticket username. Workaround: force authentication_mechanisms to what you prefer.