Giant had a closed hydraulic system at one time, if you was on the brakes for a long descent in warm weather the would stay on giving you an automatic comfort brake, the first time it happened I was struggling to pedal on a steep descent.
The Hope C2s on my MTB did that. There were rotary thumb dials that could be used to compensate but that could lead to a potentially lethal mistake...
Scary descent #1, heavy 'comfort' braking, brake fluid heating up, use thumb dials to back off the brakes, more braking, more heating, more backing off...
Reach valley floor, steep climb to next summit. Fluid cools on climb.
THIS IS WHERE I FORGOT TO COMPENSATE IN THE OTHER DIRECTION...
Scary descent #2, dive down precipitous slope, brake-brake-brake, I said BRAKE-BRAKE-BRAKE,
WTF - BRAKE-BRAKE-BRAKE!!!!!
At the last possible moment I realised why my brakes were not working and span the adjustment dials to move the pads back into their working positions...