My brake lights work fine when I start up but after a while they stop working. When I turn the ignition off and restart they work fine again. I thought it may be the brake pedal switch so I installed a new one. It was not fixed. I replaced the brake light bulbs, indicator bulbs and rear light, bulbs. I though that fixed it but no. I cleaned the rear bulb clusters and the earth points in the rear. Still not fixed. What could be causing this?