BMW E39 High beam is less bright on one side

Hey everyone, I have an electrical problem on my E39 pre facelift without Xenon. The right side high beam is less bright on the right side compared to the left. I measured 4v from the light control module when the bulb is plugged in and 9v when it's not. (Not sure what this means?) On the pin for the left side it's always 9v no matter if the bulb is plugged in or not. I tried to add another ground cable from the bulb plug to ground but it didn't change anything.

I think it could be: -the Light control module itself -the bulb plug -the wire (plus or negative side)

Thank you for your answers and sorry for my weird english