I forgot there was a quick release to disconnect the cable from one side. I just did that and felt the action by hand. The problem is definitely with the housing and/or cable and not the brake itself. They move smoothly and silently with firm spring force when they're not being pulled by the cable. I tried to flush it out with that little straw attachment on a can of WD-40, but there's not enough clearance to wedge the tip in there between the cable and housing, so I'm probably going to have to disassemble it to clean it. That tiny bit of WD-40 on each end of the housing DID get it smooth enough to spring back though, even if the dirt didn't come out. I don't have very many miles on this bike at all, so I really hope this isn't going to be a regular problem.