@David-TP
Sorry for the late response.
The links of models with the similar issue.
Archer C64
Archer C80
Archer A64
C80
My host router is EAP110.
Re315 settings

My host devices to re315: android phone, TV, PS5 all only works if I input some primary and secondary dns in the above fields (cloudflare or google, any known dns). Devices doesnt get internet access if DNS fields are 0.0.0.0. I dont know why that is. maybe a workaround i found out.
But on power outage or if re315 is rebooted, it looses only the primary and secondary dns fields. rest fields like ip address pool, lease time, gateway retains in the memory. And so i have to manually input some dns values everytime i turn on my re315 to get the host devices get internet. (I turn off them during sleephours to save power). This gets annoying, so......
Im pretty sure this is a bug and a firmware can patch it just like above Archer router cases.