the 39 is a look back fault. when you leave a terminal floor the computer looks back to see if all the rail switches have closed. If one is open you will log a 39 error. If you have the solid state mfs type switch they are prone to bounce closed then open if the magnet is too close. the magnet should be a minimum of 3/4 of an inch away. I am unsure about the 3 maybe it's telling you the 3rd switch is open. you should be able to see if the relays in the net box are all closed when you are away from the terminal landings.
