Brake light darker

Hey guys on my brake lights in the back of the car.... the left brake light is alot more dim than the right brake light. And when I turn my headlights on and hit the brake the left light stays the same but the right one gets brighter... you guys think it's a bad ground?

[ check the the place of the lamp you will find it move something to the back iam sure of that.

check that socket with another the light bulb. if it that doesnt work make sure ur ground is good. u might need a new tailight.