All error codes

router_base_network

HTTP 409 The base interface of a router cannot be unlinked

What happened

You tried to detach the first private network from a router. That network is the router's base interface: it was configured when the router was created, and the router's own address distribution is built on it.

What to do

Detach one of the other networks instead. This binding is removed only by deleting the router, so the same request will never succeed.

Retrying

Repeating this request will not help.

How it arrives

{
    "type": "https://docs.fiberax.com/errors/router_base_network",
    "title": "The base interface of a router cannot be unlinked",
    "status": 409,
    "code": "router_base_network",
    "request_id": "a277dcd1ca652c65"
}

Branch your code on code, never on the wording of title.