Attempted to take a picture, couldn't really get one that would really show you, so I googled ghosting, found this:
The image on the right, thats exactly what its like, with a little bit of "ghosting" thrown in, as shown here:
As for the STB, its just one scart, simple as that, no extenders, no splitting, nothing, and the same for Xbox too. Yes, it happens on both the Xbox and STB too. I tried connecting RW&Y to a 21 pin and using it like that, but still, same problem.