Brake force regulator

As I was now checking, it turned out that the rear brake force regulator was rusted, although the brake function on the brake test bench was very good and even. I wasn't very satisfied with the braking performance either, the mechanic sprayed that in, is now smooth again and the braking effect is really great.
PS: I assume that one says brake force regulator, has to do with the fact that if one touches the rear of the case, from the HInteraxe comes more braking effect.