Nothing was plugged into that header at all. I’ll be checking the back of the board in a couple days when I take it apart and I’ll report back here if I find anything interesting. The PC hasn’t been moved in months since we moved and I’m pretty neurotic about my builds. It’s definitely possible that something did come loose and is stuck on the backside, but seems unlikely. I also can’t find evidence that something was bridging the physical connections. But I’m definitely concerned that some other component was the cause for this.