Trendnet 200 Mbps Powerline AV Issues

[cameo <cameo@xxxxxxxxxxxxxx>]

I've been using the TPL-303E2K Powerline adapters for several years to
connect my IP surveillance cameras through them to Internet via my
home's 120V power lines. The setup worked for me better than WiFi but a
few weeks ago it stopped working. After some experimentation I found out
that the cams would still work from electric outlets closer to my router
but that's not where I needed to have them. The best guess I could come
up is that perhaps my power lines got much "noisier" recently but I
can't figure what could have caused that because I have not introduced
any new electric appliances that could account for it.
I wonder if any of you experienced similar unexplained problems and had
come up with an explanation, and hopefully a fix for it.