I installed version 15.5 today and to be honest, I'm very dissapointed. I experience a lot of bugs and a less user friendly interface. I'll share some of the problems I ran into: Yealink SIP-T38G provisioning/reboot issues: In V14, provisioning T38G phones was not an issue. First of all it's totally impossible to upgrade firmware to 184.108.40.206 and had to do this manual. After that, in V15 it's totally impossible to control a T38G with 3CX. The phone will provision just once after entering the URL in the phone, after that, it won't provision anymore. Not via 3CX interface, nor via the phone itself. I searched the internet and found some people with similar issues and some solutions (like disable the need of a certificate, defining timezone, etc) but the phone isn't controlable anymore which means we have to setup all phone by hand which is not an option in anyway. We also have T48G phones and installed them the exact same way, fortunately, those phones work flawless with reprovisioning and rebooting. We use an SBC and tried everything: SBC on raspberry, SBC on windows machine, with no firewall, secure, unsecure, nothing we can do to get the T38G to work well. Am I missing something?