Plot Holes Season 4

I just finished season 4 and am a bit confused about some of the ways the story was resolved in the final episode. Not sure if I’m missing something or if it’s just plot holes?

A few episodes before the final one, they brought up inconsistencies back from season 1, alluding that these may have been caused by the current perpetrator, saying that he’s been targeting the trio since back then. It is also revealed that the killer planted cameras in their apartments and is watching them. Neither of this gets mentioned again or resolved in any way?