So ... did pcaps on the switch, nothing, on the wired and lan side of the AP, nothing.
Once I saw a single IPv6 packet on the switch from one of the wired clients, but, just the one single lonely packet.
So I tried to change the config on the wired ports a bit, nothing.
Restarting clients, static IP, and so on, nothing.
Then, in absolute desperation and almost agony, I re-booted the AP (why would you even do such a thing.... you monster).
And I was shocked that the wired ports then worked.... shocked I tell you 🙂
I have updated the case with my findings, but Im not sure there is anything to be done now that it , apparently, works again.