Because of how IPR works it’s normal to see some extensions registered multiple times, to the same IP address / port / transport /etc. This is harmless (will have no affect on Asterisk operations), and they will expire after the phone’s next (regular) registration or expiration countdown. This normally takes 5-10 minutes but can take up to 60 minutes depending on the phone and PJSIP configuration.
If you want a more technical explanation, PJSIP tracks endpoints by the exact SIP contact header string. So even a small change in that string (e.g. changing the order of contact parameters), PJSIP will treat the latest contact (which is slightly different) as another registration. This is a known issue with PJSIP but is practically harmless.
If you wish to immediately remove old (unused) contact entries, set the max_contacts line in pjsip’s configuration to 1 (or however many phones actually register against this AOR). You can also experiment with the default_expiration and remove_unavailable settings; however, this can have other consequences so be sure you fully understand these settings before you change them.
