Fixing a PID mismatch?

[undismayed]

I changed a pokemon with pkhex and now it is no longer legal; there is a PID mismatch. I have no clue what that is but i know theres some way to calculate what it should be so i can fix it. How do i do this?

[NewHobby]

I'm not entirely experienced in this, but I do know that the PID (personality ID) of any mon is related to the origin game, TID/SID, location and level of encounter, and its IV's. If this delicate house of cards is changed in any way without an appropriate PID, the mon is rendered illegal. This means you can't necessarily have your ideal IV's for a certain mon, but you can get pretty damn close with RNG Reporter. Took me a while to understand exactly how to go about this myself, but studying this helped: