Brakes activating on their own

[dangerdred]

Car has developed an issue with the brakes, where it can't be driven more than a few miles before the brakes start to activate on their own, gradually the force increasing to eventually lock the wheels.
While driving, first thing noticed is gearbox taking ages to shift through the gears(was at 3k revs at one point before it shifted), and as the brake drag increases, car needs to be pulled over. Another clue that the issue is about to occur, is that the brake pedal seems to tighten right up, with barely any travel needed for application of the brakes. This increases to eventual zero travel at the pedal and the brakes locked on solid.
Every time it's happened so far, if I turn the car off for twenty minutes or so, and then check the brake pedal, once I can detect some travel in it, if I then start the engine, putting it in gear will confirm if the brakes have indeed unlocked their grip on the discs - enough usually to get me home. Car will then drive normally for some random period although the intervals have gotten shorter and shorter to the point now that the car is not really driveable.
I did get ABS brake pressure sensor failure error at one point, so I replaced that and all was good, until the issue returned. I'm thinking my ABS pump or module is failing?

[ainarssems]

Probably master brake cylinder getting stuck and not releasing properly all the way, had it on A6. Brakes are dragging a bit, heat up, brake fluid expands and presses brake pads harder and heat them more and so on until pressure increase so much you cannot drive. ABS sensor was probably OK, it was just showing pressure when the car was not expecting any.