These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Sequelitis: The sequels border on being short films, and are padded out by footage from the previous installment(s) shoehorned in.
They also tend to forget certain plot points, right down to the third movie getting Lacey's name wrong, as well as her uncle and aunt's family affiliation, which the movie says it's her brother and sister.
Narm: Do we even need to explain this? Especially considering one of the most silliest deaths is a boy getting crushed by a window.
Bonus points what follows after: Death by cabinet door.
They Just Didn't Care: The first film showed that any part of the mirror can com-bust into flames with a hint of water being on it. The sequel completely ignores this. Not in a retcon sort of way, but it has stock footage of the first movie. This includes scenes where the mirror does com-bust when it is touched by water!
In the third movie, they got Lacey's name wrong, referred to her uncle and aunt as her brother and sister, and even shoe-horned a connection with the first movie by claiming that the psychic told Lacey's brother about the mirror spirit's weakness, even though anyone who witnessed it can piece the two to two together (which is how the first movie ended).
What an Idiot: In the sequel, Lacey decided to keep that one mirror shard that was not destroyed, who should know full well that it is capable of causing death onto people by merely shinning light towards the victims! After all, she (somehow) knows about the lovers who were killed. That and it is capable of possessing people, something she has been a victim of!
Could Have Avoided This Plot: On top of this, she talks about the whole events (including a pointless dream sequence, and two series of deaths she could not have witnessed, let alone be able to explain in perfect detail) to a group of people who decided they wanted to make a movie about it. This ends up getting almost all of them killed by the Butler, who was possessed by the mirror shard Lacey kept. She even admitted to the audience that the mirror spirit was seeking revenge to those who dared to exploit it's story. So basically, in order to have prevented their deaths, she could have just simply kept quiet! Better yet, why not just destroy the remaining shard?!