delete the json player, the game creates a new one, loads your controller and your graphic configuration again, the connection I take it by default does not give me problemsI have this problem as well, it happens very random, I just try to join the server over and over again until it works. One thing I did that might have helped me, I changed the network settings to: UPSTREAM 10.0 Mbps. DOWNSTREAM 20.0 Mbps. It has happened less often after I changed these settings. Hope this helps you.
pd.-eliminating the player json removes many problems of falls and failures, let the rfactor make a new one