This started off as an experiment for triggering func_ladders, but I scrapped that and ended with a ladder fixed in position. Ladder now does not work except when crouch jumped into, and climbing to the bottom using this method sticks the player. Noclipping during play is advised, because there is no other way to get between the two areas. (Granted, the ladder doesn't reach up far enough, but I will fix that.)
To fix this, rebuild the area immediately around the ladder, and/or convert the immediate area's brushes to func_walls.