Brake lights not working at night

[JackWinson]

So I have a 2007 Mk5 GTI and I’m having a problem with the tail lights. During the day the brake lights work fine, the outer semi circles light up when the peddle is pressed. However, as soon as the side lights or night lights are switched on you can’t see if I’m braking or not. My understanding is that the night lights are a full circle and when you brake they get brighter. My lights are already as bright as they’ll go when you switch them on so there’s no difference when the pedal is pressed. Does anyone know what this might be?
I have changed fuses and made sure the bulbs are right but no luck.

[blingsta]

sounds like the brake switch

[mjmallia]

If there is no difference in side light and brake light brightness, it sounds like it need to be plugged in with VCDS and the settings checked for the side light dimming as they can be adjusted.......I turned my sidelights down when I added LED bulbs due to being too bright on 20% power compared to the brakes.....knocked down to 10% to give the same light as a filament bulb for me.

Brakes are usually set to 100% and sides to 20%