My Negative G rear brake has been acting up. Earlier this week, out of nowhere, the rear brake would not release. By that I mean the return spring wouldn't return, so when I would brake it would actuate but then the arms would not release.

I tried replaceing the cable and housing, it didn't help. So after messing with it for awhile I took it to my LBS and the mech put another new cable and housing in, and messed with it for awhile and finally got it to work.

Then today, during the first stage of stage race the brake started to have the same problem again.

Any suggestions?