I use mains networking / 'powerline' for most of the house (thick walls!).
Recently, one PC has been having network outages. In trying to see what's happening, I have installed a script that pings Google every five seconds, noting when it fails and then when it works again.
On this PC, it's almost completely perfect. (Almost as good as the Pi connected directly to the router in another room which is totally solid.) One fail in a week level, coming back within five seconds - a single failed ping a week, basically.
On the PC in question, it fell over forty or so times yesterday, with some of the outages lasting over five minutes. It's plugged into a different mains networking adaptor to the first PC, but the same as...
.. another PC. It falls over nearly as often, but only for five or six seconds at a time. A series of individual failed pings, basically.
Those two are running the same Ubuntu MATE 22.04 on similar hardware. I've tried adding a USB-Ethernet adaptor to the problematic one, and that hasn't helped.
If I swap the mains adaptor plugs, that doesn't change things. It's ultimately been plugged into the same mains socket for well over a year - this was set up shortly after March 2019.
Any suggestions as to why one would stay fallen over for minutes rather than a second or two?