no lights!

While switching from main beam to dim, sometimes everything goes black, but if i push the switch further it comes back on. Last night. It didnt come back on and I ws totally in the dark. Just the headlights and side lights on 2002 defender td5. I was just outside my home so got in on the hazards. I could find no fault with the fuses. This morning when I checked them again, everything was back to normal!
Has anyone else experienced this?