We have been having an intermittent issue on our VoIP phone system since it was installed. I'd rather not mention the brand initially, as it sounds like we're the only customer of theirs in the world that has this issue. I.e. I don't want to tarnish their (I assume) othwise good reputation.
The problem we have is when you answer a call, there can be a delay in audio of anywhere from 2 seconds, up to over 30 seconds. Neither party can hear the other, it's dead silence on the line. There's also no audio loopback; you can't even hear yourself talking to them.
The call could be answered by Group Pickup, transferred to your extension by someone else who had answered the call, or even just an internal call between extensions in the office.
It happens to at least 6 of our 24 extensions. I say at least because some staff don't get many calls, so they may be having smaller delays and not noticing.
I have swapped network cabling, the PoE switch, phisically segregated the phone system from the rest of the network (not just made VLans), swapped some phones for new ones, even replaced the main phone system boxes that "do the work".
If anyone has any suggestions of other things to try I'd greatly appreciate it.