Single bad lan port?

Seems I have a bad port - LAN3 only connects at 100base-T half-duplex. The problem stays on the port, not the cable, if I swap cables and devices around. It’s always LAN3.

Is there any kind of config issue that could cause this, or is it likely a hardware issue?

I don’t see any settings specific to that port in /etc/config/networking and swconfig shows the speed but apparently doesn’t allow setting the speed, as I always get Operation not supported

Port 3:
    mask: 0x0000: (3)
    qmode: 3
    pvid: 1
    link: port:3 link:up speed:100baseT half-duplex

Let me know if there’s anything else I can test or output to provide, thanks!

That sounds like a HW issue to me, but I’m not a HW person. (Still, I’m using an Omnia with this HW deficiency on multiple ports.)