Other mistake: When Dennis jumps out from behind the glass wall shield, leaving Arthur behind it and The Hammer and Juggernaut ghosts attack, Arthur bangs the glass yelling as if he can't get out; but the wall shield is only propped up, unsupported and should've fallen straight forwards when he thudded his fists on it.
Continuity mistake: In the scene where the psychic and the father are walking through the halls carrying the plate of glass as protection, you can see the trees outside blowing in the wind. Earlier, they showed that all the windows in the house closed up, making it impossible to see outside.
Other mistake: In the scene where Cyrus's Nephew first sees the kids in the in the machine. (1:18:45) The shot goes back and forth from him to the machine. The first 2 time the glasses are fine the last shot (1:18:550 The prescription inserts in the glasses are crooked. Bad editing.