TivoHD weak ethernet port

Here's an odd one:

I've got a fairly old TivoHD. For several years the ethernet port worked perfectly. The connection between the router and my Tivo has two switches between them. One switch up in the attic, the second behind my media center.

A few years ago the Tivo would lose connection to the web. I was able to get it sporadically working by connecting only the Tivo to the cable coming to the switch at the back of the media center, which cut connectivity from all the other devices. Eventually that stopped working as well.

However, the Tivo Wireless Adaptor works well for about a month. This plugs into the ethernet port though.

So I'm wondering if I have a bad winding in the transformer of the Ethernet connector in the Tivo. Has anyone had a problem like this? I have no problem with getting a replacement and installing it. However, I'd like to know if this would be likely to solve the problem.

Or, I could just connect the wireless adapter again, but I don't like having so many devices be wireless when there's a wire right there.