The sole purpose of Copaxone, Rebif,
Avonex and Betaseron is to slow the progression of the disease
and reduce the number of relapses. If you look at the studies, people on these CRAB's still have relapses, they just don't have as many relapses as people who are not on a CRAB.
So it should not be a surprise to any of us on a DMD when we do have a relapse. The CRAB should be making it less intense and shorter in duration, hopefully.