Deficiency of the brake power amplifier

Hello I have a Ceed 1.4l Built 2007 Is there any information about the failure of the brake power amplifier? Today it happened for the second time that I had no brake power support and I had to bring the vehicle with the hand brake to a standstill. The first time it happened some time ago. It was double-digit minus degrees. I didn’t think about it at first. At the temperatures it can happen. Who knows what was there. Today we have 10 degrees plus and it happened again. After about 70 meters I had to stop on the road before driving in. I wanted to brake and nothing happened. The brake pedal was “stone hard” . Even when I stepped on it more strongly the car did not brake. I had to make it stand with the hand brake. Since I wanted to clear the driveway I then, a few seconds later, drove a piece to the side. Then suddenly the brake worked again. Brake pedal was “soft” again and the vehicle braked again. Has anyone ever experienced such a thing and has a repair been done?