Enahs,
It sounds like you have isolated the problem, now you need to fine the real cause. This can be an issue.
I used to work in quality for a Detroit first Tier. It became clear to me that unless quality programs are forced on most manufactures, they will not embrace them. The fact is, that there is very possibly a component of that brake that is the problem. It might not actually be out side of the manufacture's tolerances, but those tolerances may be quite worthless. Finding the problem part can also be a big problem. There is also no reason it has to be just one part.
Matt