fix #4529

lib/network.py

@@ -529,6 +529,7 @@ class Network(util.DaemonThread):
         self.auto_connect = auto_connect
         if self.proxy != proxy or self.protocol != protocol:
             # Restart the network defaulting to the given server
+            with self.interface_lock:
                 self.stop_network()
                 self.default_server = server
                 self.start_network(protocol, proxy)