It was not sabotage of the Shuttle. It was, apparently sabotage, of a unit to be installed on the space station. The unit’s purpose is to take data from strain gauges mounted on the ISS truss and integrate them into the TM being sent to the ground, so they can do a study on the stresses that occur on the ISS structure. It is not a unit that is vital to the safety of the ISS or the Shuttle. The ISS has done without it since it was first put into service, and it could probably do without it for the rest of its service.

As to whether it was really sabotage is still to be determined, or at least revealed. The way they were talking about it, it seemed they were fairly sure it was sabotage. This is only speculation on my part but it could be a disgruntled employee who was being laid off, or it could be the result of a misunderstanding in procedures at the contractor. Could be as simple as an error in a drawing. If it does turn out to be deliberate sabotage then someone is in a great deal of trouble. It wouldn’t be the first time this has happened.