From the little checking I had time to do it seemed to be all four of them. It's not really a problem because the receiver doesn't do any upscaling for the TV. And the sound is much the same with the optical cable. I'll still pull it out and have a look. When I was checking I could get a signal when I pushed on the port. Makes me to think a bad connection.
I think a purist audiophile would say the optical connection is better than HDMI. I’m not sure about that though. Depends on the audiophile. It’s one of those things they love to argue about. Like vapers and mech vs. regulated.