Network scenario:
BR -> router -> leaf

BR knows that leaf is behind router, however for some reason the leaf node goes missing and router drops it from its fib (e.g. by router reboot, or clock drift between BR and router so that router drops the route before BR does).

Now BR will forward packets to leaf via router, and since router does not have leaf in its FIB it will pass the received packet along its default route, which is BR. Now the packet starts bouncing until TTL is reached. This will lead to excessive power drain and occupying wireless bandwidth for no good reason.

IMO there should be a check somewhere in the routing decisions that drops a packet instead of forwarding if the routing decision is to forward it to the same link layer address from where it was received.