Hi guys, I have had an IoT hardware (Ikea trådfri router) connected to the eth3 port of my HAP AC2 for a while now (3+ years).

A few months ago i started to have issues with it, after updates or restarts of the main homeassistant server, the server (homeassistant) was starting to lose connection to the trådfri router, all connected with ethernet cables. After a few restarts of the trådfri I managed to get it back up. One month ago I was not able to solve it by hardware restart, so I did some fault search and connected the trådfri with the same cable to nother port and started to work again. Connected it back to ethernet 3 and it stopped.

All the lights seem to light up and I have not changed any configuration settings for the ethernet 3 port, any way I can fault search this and try to fix it?

If the problem starts to develop (from mild one to a more serious one) without any changes in configuration or software, then this likely means a hardware fault ... such as a crack in cold junction which is getting bigger due to thermally induced material ageing. And that kind of problem is hard to diagnose and fix. So if you can spare a port, just connect trådfri router to different port (and tape off the failing one not to use it again).

Another problem might be ageing power adapter (but I'd expect the effects to show on all ports equally), so if you have a 24V 1A power adapter lying around, you can replace it and see if that helps.

Ok, thank you, I was afraid that would be the case. Thank you for your reply.