Most of the time outside people can't hear the issue but it has happened. I've made a ton of test calls but it doesn't happen often enough for me to hear it so I have to go on what they are telling me. It's also why I'm thinking QOS because I'm not using their PC while I'm on a call.
This is not expected, especially on SPA phone to SPA phone calls. Is your switch running the latest firmware with the Auto Voice features enables (upgrade and factory default to the latest firmware to auto enable). Are your phones on the voice subnet (default is 10.x.x.x network)?
If the problem is just on calls over the FXOs, then suggest running the Impedance Matching tool for each port. This is found on the FXO page of the UC320W Configuration Utility.
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