Hi there I hope someone has an explanation for this weird behavior: We have two separate 3CX installations using Yealink T22P phones. Until upgrading to latest 3CX version and latest Yealink T22P firmware, things were ok. After the upgrade, we have the following behavior that occurs after a while: - Phones stop responding to Remote Control commands (CTI mode in 3CX) - The phones web interface also becomes unavailable After a reboot, the phones behave normally, until after a while when they lock down again. We have tried using the phones in various configurations - provisioned by the 3CX system or manually configured. We made sure remote control is allowed from "any". It seems to me that the firmware pushed by 3CX (18.104.22.168) is at fault - either causing the phone to blacklist the local subnet (or any IP) or by simply crashing the web server after a while. I would guess it is the latter as a nmap scan does not detect httpd behind the ports 80 and 443. I find this issue really disturbing - regardless of the fact that the phones are not supported anymore. Any vendor has an obligation to make sure older equipment can still be used in the long term and the fact that the latest versions (3CX + Firmware) are basically rendering the phones useless is deeply upsetting.. We did extensive testing and it looks like the firmware version pushed by 3CX is heavily customised and causes this behavior. I wonder if someone else is experiencing similar issues or if someone has any hints into how to fix it. Moving beck to a previous 3CX version is not an option due to ICT compliance requirements.