number plate lights not working
 

So my number plate lights, aka the license plate lights. Are only working sometimes. I've tested the contacts where the light housing go on and that isn't the issue. I've traced the wire from the trunk to under the rear seat. That wire is sometimes getting power and sometimes isn't. The lights either blink on or off. And there isn't power going to the lights on the trunk lid itself when there isn't power at the wire I'm checking under the seat. I have no idea where to look to solve this issue. Thanks.