Vin

Here's Yealink technical support: Sorry that we didn't know about this report here until now. This is a random issue may happen in some special environment. We are not sure whether it makes sense but we tried to fix it on our point. There are V51 beta firmwares you can download to have a try: T28 V51 Beta http://www.yealink.com/fae/2.51.0.6.rar T26 V51 Beta http://www.yealink.com/fae/6.51.0.6.rar T22 V51 Beta http://www.yealink.com/fae/7.51.0.6.rar T20 V51 Beta http://www.yealink.com/fae/9.51.0.6.rar V51 change log http://www.yealink.com/fae/Yealink SIP IP Phones V51 Firmware Change Log.rar However, this bug fix is not declared in the changelog.