I have the same issue with my 2006 K1200GT with 32,000 miles. I purchased this bike 10 days ago on eBay, flew down to Tampa (FL) to ride home back to Richmond, VA. The previous owner had a service done with 'all fluids' about 2 years ago and rode the bike only 600 miles since that service.
50 miles after leaving Tampa I had the Brake Failure fast flash with red triangle and noticeable lessening of brakes, front and rear. I stopped for a few minutes and when restarting the bike the fault had gone (reset itself?) and the brake were fine. This happened a few more times and I decided to have the bike towed to the nearest dealer in Jacksonville, FL. Before the tow truck arrived I connected my GS-911 and read two faults - high pressure in front circuit and another (can't remember, but seemingly unrelated).
The next morning I presented the bike to the dealer and they went thru the usual diagnostics and found all parameters within spec. Had some discussions with service mgr and decided to get back on the road back to Richmond (630 mi). For most of the following 400 miles I had the brake failure flashing and sometimes had normal brakes, sometimes less than normal. Every stop reset the faults, and they reappeared after 10-20 miles. The last 200 miles - no faults, brakes worked fine.
Today I took the bike out for a 20 mile ride and the flashing started after 10 miles. If I held the front brake lightly for more than a few seconds it went 'limp', lessened brakes. But if I tapped the foot brake, the front brake returned to normal. Hooked up my GS-911 and read a single fault - front circuit pressure too high.
I have learned that Module Masters in Iowa can now rebuild this servo ABS unit for $750 with a 5 (?) year warranty. They replace the servo motors with more reliable units. This is way better than buying a 'new' ABS unit from BMW for $2700 (plus labor to install, totaling nearly $4000) - INSANE! And this new unit contains the failure-prone servos.
But I also learned from my local BMW dealer service mgr that worn brake pads and/or low fluid will trigger these faults. So I need to look closely at my brake pads and check the fluid levels. The ABS unit actually has its own two reservoirs and the fluid from these connects to the front and rear brake calipers. The front and rear master reservoirs only send fluid to the ABS unit. So there are actually 4 reservoirs, and 4 circuits.
That's all I know at this point. But I like this bike very much and plan to solve this problem even if Module Masters is in my future.