Its Contact holds pn-prid=...:voip&...:remote, and PJSIP_DIAL_CONTACTS passes that '&' through, so Dial rejected the whole device list and the call dropped for every device of the user. sp-sub-contacts walks the AOR's contacts, drops pn-* params and FILTERs the rest. call-test registers a phone with such a Contact and checks it is rung.