I think it’s more related to wifi, than WAN. This morning, when it failed, I have connected the laptop with a cable and It got an ip. With Firefox, I could access to the web ui, but with safari I couldn’t. To me everything is very wired.
This is what you described this morning:
After some weeks it happened again, two times in a row. I have disconnected one node but it didn’t work. I connected the cable, and the laptop got ip, but I was unable to access to the internet either. Perhaps it’s time to to change the router.
So your LAN was working properly yet you had no Internet (WAN).
I read through the thread and it lacks a lot of detail of your problem(s). Continuous mode should not get you blocked. It simply means the router will retry DHCP requests if the first one(s) do not work. Aggressive mode can result in your ISP blocking you and it's rather rare which is why it's the default.