You will generally have less issues over a wired connection than a wireless one.
The first thing you should try is swapping the network cable for a new quality one and similar with the patch cable to the switch port (and any horizontal cabling in between). These can often cause you issues if you happen to be using a poor quality cable or connectors.
The next thing you can check is what the traffic across the network from where your Edge95 to the far is is like - are there any large latency hops, or congestion happening anywhere? Are you able to use a lower call rate to see if this helps your call quality?
Given the Edge95 is an End of Support device (they went End of Support on 31 May 2018), I'd highly recommend that you look at replacing it with something a little more current and supportable.
Wayne
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