Did anyone notice issues with Fritzbox 7390 devices? When upgrading from 4.0.1 to 4.0.7 some of these devices fail to register after some time.
They keep trying to reuse an old nonce and ignore the new one in the 401 response to the REGISTER. It will try 11 times to register with the same cseq, nonce and nc, then it will try to register (11 times) with cseq+1, nc+1 and still the old nonce. So www_auth fails with -4: stale nonce. I could find anything in kamailio auth module to accept this behavior.