Router intermittently losing WAN access

I just installed OpenWRT on an Askey SAX1V1K / RT5010W-D187-REV6, and factory reset it.

I've not yet even configured WiFi, but my router is losing WAN access (LAN is ok) intermittently for about 1 min.

The only error I see in the system log (verbosity is set to "debug" is this:

Sun May 12 20:57:11 2024 daemon.warn odhcpd[2014]: No default route present, overriding ra_lifetime!

Does anyone know what this might be?

That message is not related to WAN, it says there is no dhcp6 connection, thus dhcp6 server on LAN will not serve route to the internet.
logread -e netifd will filter actions to configure network interfaces, hide public IP addresses and your MAC addresses if posting fragments of it.