This is why there are such great relations between unions & management & vice versa.
Everybody, on both sides, knows that the person can't perform and should not even be employed, but damn all that, I'm union, I'll fight to keep the job I am unqualified to do. Why? Because I can.
It is exactly the same as people sueing ladder companies when they fall off a ladder, or sue McDonalds when they get burnt spilling coffe on thier crotch. They want something for nothing, and take no personal responsibility. I am OWED this. Bull. You fall off a ladder or spill your coffee on your privates, just admit you are clumsey or stupid & move on.
If you clearly cannot do a job, get a job that you can do, elsewhere. I personally would be embarassed to file a grievance for this.
Punt.