At some point we began experiencing blank voice messages, no music on hold and no recording beep tone. Also occasionally incoming calls come in without audio, i.e., they can hear me but I cannot hear them. All of this occurs on a random basis but is happening more frequently. I have 3CX v15.5 running on Windows 7 and using Yealink T42G and T46G phones. Has anyone had these type of issues and resolved them?