I've configured a host with a low level discovery rule, where the SNMPv3 'auth' and 'priv' passwords were different. The low level discovery rule fails to run (it throws an "SNMP error" in zabbix_server.log).

As soon as I changed the 'auth' and 'priv' passwords to the same value, I was able to get the discovery to run.

if you guys need any more info from me, please feel free to let me know (or mark the ticket NEEDINFO or whatever)