That collective bargaining agreement is representative of most CBAs under the Railway Labor Act for unionized airline employees. The grievance provisions are virtually identical to those I worked with when I was an ALPA representative.
EDIT: In the pilot contract I worked under we had a provision that a pilot would not be required to pay for any equipment he/she may damage in the conduct of his/her duties. I don't see that provision in the linked United FA CBA. So, in theory at least, the company could bill the FA for the $20,000 plus expense of restoring the slide.