My 2008 K1200GT had a similar failure 2 days after I purchased it (used).
Intermittent BRAKE FAILURE Light...eventually steady
Bike had 7,000 miles.
Fairly common on these machines.
Sent mine to Module Masters...
$250.00 + return shipping.
It's fine now.
The unknowing may spend $2,000 USD or more to have their local dealer replace with a new ABS unit.
I'd bet it is the same sticking brushes malfunction that is outlined with a DIY fix via a YouTube video on the subject (sounded like a gent from your side of the pond).