It was only a half-joke, as mechanism detecting type of plug connected (headphones, microphone, TV-out) is based on OHM value between mass and 3th part of jack plug. On pure headphones, 3th part is non-existent, so resistance is 0. ON microphone, resistance is ~infinite. On TV-Out - while connected to TV - it's 75 Ohm.

So, if You get TV-Out enabled popping out while plugging-in headphones, it seems like it happen when plug is only partially insert - resistance between 1st or 2nd part of jack and mass (or 1st and 2nd part, it depends on how much plug is inside) is triggered by detecting 75 Ohm resistance.

I can't tell why it's happening - it doesn't in my case. Maybe Your plug/cable is damaged, and there is very little connection between 1st and 2nd pin (left and right channel), generating ~75 Ohm resistance? It's 7-8x higher value than direct (even thin) connection, so You could not detect it while using headphones.

/Estel