I will dig into that in the AM. What I did find was that the network.disconnect_peer call ended up being the root cause.
@rpc("any_peer", "call_remote", "reliable")
func return_login_response( player_id, result ):
print("Sending login response to client %d" % player_id )
rpc_id(player_id, "return_login_response", player_id, result )
await get_tree().create_timer(1).timeout
network.disconnect_peer(player_id)
This ended up resolving it.