Continuity mistake: When the killer rips his mask off to expose his face to Maggie, his eyes go from brown to yellow between shots. It is explained later that his yellow eyes becomes brown thanks to colored contact lenses, but the killer does not remove any contacts when rips off his mask.
Continuity mistake: When The Possessor puts a mask of Toby on, in front of Maggie, he then takes it off and puts it on a metal tray. He then takes a second mask and puts it on. then, when he goes to put the second mask down, the mask of Toby, which he left on the tray, is now placed on a foam dummy head.