might sound a bit strange..
but when i installed a whiteline rear swaybar, i was 'testing' it right afterwoods at the local 'racetrack', h/b light came on and stayed on. I checked underneath, swaybar had been smashing h/b cable on one side. I have since got droplinks and made up a little clamp to stop its sideways movement.
Anyway, i checked over sensor, mounts, fluid levels, re-adjusted it for good measure.. then took the lamp out of the dash, it is not on anymore.
No idea if that helps.. or if the standard rear sway would come across that far.