Help with lights

[Sinn]

Im having a problem with my nav and anchor lights syncing together. I have a 3 way switch. Im being told that in the up position (nav) should be nav and anchor light on and in the down position (anchor) should only be the anchor light and the middle position would obviously be off. My problem is when in the off position my nav light is on and when in the up position only my nav lights are on and when i put it in the down position my anchor light is on and my nav is on but the nav light is very dim. I wouldnt think it would be bright enough while being on the water. Does anyone know what is going on here? Possibly a ground issue?