Back right light stays one, all day all night even while the vehicle is on/off.
In most cases that is caused by a defective SAM module. You will need to scan the car with a advanced scanner that can read codes from the SAM modules. I belive the SAM unit will need to be coded to your car, so you can't swap it with a used one. Not 100% on this as it varies between MB models.
Let us know what you find out.
What have you tried so far?