There was no evidence of binding; rather, the mechanism appeared to be blocked from moving at all. I spent a long time yesterday trying to troubleshoot it. What seemed to be the issue was that the bell crank (and associated linkage) was sitting in such a way that the linkage was trying to pull...
I can release the parking brake, but then it remains in the down position - even using more force than I am comfortable with. Obviously, now I am unable to start the mower. I can't find any information online about adjusting this brake; the parts manual diagram isn't much help in figuring this...