Throw-out bearing

Throw out bearing can fail from age, because of someone lightly riding the clutch enough that the bearing is spinning all the time or there could be an issue with the pressure plate fingers that made the bearing engage at an angle.

As for changing the fork, if it is damaged/bent or the pivot is worn out then change it. If you are already in there and the clutch hasn't been changed I would do that just to keep from having to take it apart for a long while. Plus you can likely get an upgraded clutch with all the pieces for less than buying the individual parts. Don't forget to resurface or replace the flywheel.