1990 190E - Child Safety Switch causes fuse to blow?

[Holson Adi]

I have 1990 190E 2.6 and lately the fuse for the right front and left rear power window breaks as soon as the child safety switch is connected.

When the child safety switch is disconnected, all four windows work correctly from the console switches.

I have the wiring diagram and have thus isolated it to somewhere between the left rear window switch on the console and the left rear window switch on the left rear door card.

What I noticed at the left rear window switch harness was that the illumination wire (grey/blue) does not register any voltage between it and the ground on the same harness even though the right rear side does (yes the child safety was switched 'off' - that is let the rear switches control the windows')

Any other pointers?