I know this may sound a bit out there as a possible cause, but, early brake caliper perches were not machined from billet plate stock. Many were what appeared to be cast.

I know from experience that some frames need these older style perches, or have a current billet style modified.

With a billet perch, it does not have raised bosses in the bolt areas. This can make the perch seat at odd angles or positions.

FWIW, we have Avid BB7, with old style perches on our Co-Motion with a Wound Up, they work fine. Just took a look at our fork and I would expect a billet perch to seat properly, but some times things don't work as planned.

PK