We consistently have an issue when provisioning phones, on the local network, using 3CX Phone System Management Console v11.0.28976.849. It also occurs when a phone is powered off/on, which similarly causes the phone to boot and contact the 3CX server to provision itself. The problem is that provisioning phones instantly causes router lockup, which in turn results in internet outage and downtime for the phone system until we do a hard reset on the Draytek router. The phones are Grandstream GXP2110 (initially with firmware 220.127.116.11 and now with 18.104.22.168) and the router is Draytek Vigor 2920n with latest firmware 3.6.3. I realize that the likely culprit is the phone itself doing something weird, but I can't be the only one using 3CX software to provision a phone while using a Draytek router. So, hopefully someone here will know how to find a solution.