C5 X7 brake light switch harness

[Cynthia13]

2013 C5 X7 Intermittent ESP/ABS warnings (as per earlier post on that topic).
Brake light switch replaced (no change) but apparently the switch harness can be troublesome and could be the issue. Is it necessary to change that part of harness complete (and where does it run to from switch) or is it likely to solve the issue using the kit which includes an intermediate harness length?
Thanks in anticipation
Peter and Carole

[Kees]

If you replace the switch with a new one, then the problem is something else, because when the switch is older, then the contacts inside are burned in, this gif spikes.
And the modified harness is no more then a piece between the switch and the original harness with a damping diode inside.

[Cynthia13]

Thankyou Kees, that's helpful. We'll continue delving.
It's quite annoying that most garages don't have the diagnostic to go in deep enough. Mark's responses to our original post were extremely detailed and helpful so we're working through them.
Cheers, Peter and Carole