The biggest mistake Jun is doing in both games and fanfics is decisions or decision making.
Before Tekken 3, Jun instructs her son Jin to meet Heihachi in case if something happens to her which they are attacked by Ogre. So Jin follows his mother to see Heihachi to be trained after he believes his mother was dead.
In Tekken 8, she blames herself for her wrongful decisions after learning that Heihachi had endangered her son which angers her in her special interaction with him on her Amatsu Izanami Rage Art.
In the fanfics within the third part of The Strangest Things: Purging of Evil, Jun convinces Hunyo to return as a paranormal investigator which he accepts because of both Jin and Rhima who wanted him to come back on his old job. But she finally realized her biggest mistake after sensing demons in the real world is much worst than in their world. Like Hunyo says, Jin and Kazuya's devil forms can't survive against most powerful demons in the real world. She eventually apologizes to Rhima for her decisions to convince Hunyo to return as a paranormal investigator and realizing his reasons of quitting that job.
I have to say this that Jun can make up for her mistakes.
