Late last year we had an issue where our inverter panel reported an “Unknown Fault”, showing garbage on the screen. I reset the inverter, and the fault went away.

Recently, I had the same “Unknown Fault” and garbage display… but resetting the inverter didn’t solve it.

I looked at the inverter itself, and fiddled with the network cables, and the issue went away… for a while, but came back after driving, so obviously something was loose:

The phone line splitter was a prime suspect, and indeed it was crumbling:

So I bought new phone line splitters; I thought that one with a short cord would be more resilient:

Installed:

That did the trick.