Fix-it - Fanlore
https://fanlore.org/wiki/Fix-it
Fix-it fic, or "fix fic", is fanfiction that changes something about canon that the fan writing the fic wasn't happy with. This can be anything from explaining plot holes or inconsistent characterization to bringing a favorite character back from the dead.
In some cases, fix-it fic is written to "fix" fanfiction rather than canon. This is most effective when the piece of fanfiction being "fixed" is sufficiently well-known that readers of the fix-it story will recognize the new story as being in conversation with the previous fanwork. This type of fic is also called Responsefic.