A big part of Legends of Windemere: Family of the Tri-Rune deals with handling past mistakes. One of the main characters made a big mistake in a previous book and now they’re about to face the consequences. Part of the problem is that people despise the character for those events, so there’s a lot of complication in here. This is even bigger than Luke facing his past in Allure of the Gypsies. He earned all of the negativity that he got for running away from home. This time, the person has already been suffering from that fateful decision.
When writing a series, you can use a lot of long-term foreshadowing and keep a few questions in the air by the end of a book. This does have the risk of some readers demanding closure when you have it planned for another book. Anyway, a series always your characters to make mistakes that seem minor in the moment and roll into a major plot point in a later book. For example, destroying a thieves guild and letting one young member escape. That character can come back as a new hero or a villain depending on how you work.
Personally, I love when past mistakes are revisited. This allows locations and characters from the past to be brought back. There’s some nostalgia that comes with that even if it’s under bad circumstances. Honestly, I can’t really say anything other than I love foreshadowing and going back to the past in a series.
So, what do you think of books that return to previous locations to clean up past mistakes?