I have the same problem. Disconnect the cable from the caliper and make sure it's not the caliper hanging up. If its not, replace the cable. They're only 17 a piece from GAP.
Anyone have an idea as to why only one of the cables for my e-brake won't release all of the way? It started with my e-brake being so out of adjustment that the cables fell out of that cup/hanger piece. Now that I had it all back together one side will not release all of the way unless I push the cable back in by hand. I've tried lubing the cables and the e-brake hardware on the caliper. Still nothing. Any help/ideas would be greatly appreciated!