Hi. Without wanting to sound like a complete plank, I managed to lock up my rear today, I thought that would not be possible with ABS??
Joking aside, I had same thing happen to me, similar speed. On a section of shell grip when car in front decided to stop for a seagull in the road.! Hasn’t happened again but I did wonder at the time.
Did you feel the classic pumping through the rear brake lever ? Whilst not at that speed, I have had the ABS kick in on my rear brake but not so as to fully lock the wheel. Whilst the sensor might not be duff (no error message ?) it could probably do with a good clean as could the ABS ring bolted to the rear disc. Andy
2014 M1200S I have done the same 3? times? always felt the pulse. All downhill into turns. Once brakes alone. It wasnt much, you could feel it get squirrely... Twice while downshifting... Still not much, just some wiggle and then it stopped. I didnt think I could overcome the ABS, let alone the slipper clutch. I was kept safe though... Rex