When we supply juice to brake lights both filaments in the brake light bulb light up. This is ok with headlights off. But when headlights are on, both filaments are lit, so only difference is the central brake light. So if headlights are off you see brake lights work normally except they are too bright. When headlights are on, just the central light goes on since brake lights are already on bright. I drilled drain holes in both sides. Put a bead of silicone around gasket. Changed all taillight bulbs. What is next?