Last Friday stream Ryan mentioned that when his internet connection fails he can still hear the others but they cannot hear him.
This assumes that what he is resting is the ISP box that terminates the fiber and that fixes the issue.
I believe that the connection is a fiber to the home setup that is probably a PON network setup.
These have 2 different TDM domains one at a higher bit-rate for client download and one lower bit-rate for client upload.
Since some incoming connections stay up,at least UDP streams for voice,but the rest of the call cannot hear him it might be that the upload is getting out of sync.
This is a hardware issue,clock skew or some other issue with the device.
Recommend asking the ISP to change the box,or if they refute and u have the patience a little high voltage should force them to.
If the issue is the actual router he is using just go Pfsense or Mikrotik,the latter have 10W solutions that can route 1Gbps and have 200Mbps Wireguard capability(HapAc2).