Is there a separate ground to the rear brakes somewhere? My brake lights work 98% of the time but then I'll have someone drive by and say there out or one side is out. Trying to eliminate possible causes. Thanks
Also note that the contact between the actual bulb socket and housing are two different pieces and corrosion between the two metals can cause a loss of ground to the bulb.
If you look close you can see the parting line between the two.
I have solved this problem by drilling and putting a small screw where the two metals come together.