if you look from underneath, in front of the handbrake back plate, right at the bottom of the extension between t box and handbrake there is a small hole, angled back and up at an angle of 45degs. This invariably gets blocked and allows a build up of oil which then gets onto the brakes. you can normally clear this with a small screwdriver, but in fairness, I found the best option was to remove the handbrake mechanism, the back plate, the oil spinner cover, wash them all in petrol to clean them - it becomes easy then to find the hole and clean out all the crud - so that if the Tbox does leak, the oil can escape.