If you find that SYSAUX is growing and its size is too big, besides figuring out why this has happened (bug, some purge job disabled, or some structure problems in objects), you need to find the objects and purge them manually.
This is a companion discussion topic for the original entry at https://blog.toadworld.com/2017/11/15/sysaux-and-purging-big-objects-segments-manually#:~:text=Two%20components%20of%20Server%20Manageability,Optimizer%20Statistics%20History%20(OPTSTAT)