When a client and server are connected using a direct address the client has the server's address stored in the "best address". If you now restart the server and ask the client to create a new connection to the re-started server, which is using the same EndpointId but a different IP bind address, the connection is very slow.

The issue is that the "best address" is still known and is considered valid for 6.5s. So even if the new connect call is given the new correct IP address of the server, it will keep sending to the previously chosen "best addr" until the 6.5s time out. Only then will it fall back to the relay and manage to re-establish a connection.