Stiff brake on motorway

Hi, I had a little issue this week on the motorway and found the same problem in the Skoda Superb forum. You can read the text below.

I´ve not had any other brake problems and it has only occured one time, but it´s not nice when you think the brake is stuck :-)

"I now have a disturbing new problem that nearly gave me a heart attack on the motorway today.

When the cruise control has been on for a long time and I brake, the brake is stiff and has to be pressed a lot harder than normal. For a split second it feels like it is stuck which is scary when you are travelling at 70mph+ I can tell you."