Near the end of the film Jeff is seen putting a blanket around his mother to comfort her and in the very next shot she is not wearing it.
A fire drill does not trigger fire sprinklers as shown in the office scene of this movie. Sprinklers are activated by heat, not by the fire alarm system.
The phone rings while Jeff is looking at a "knive". Jeff picks up the cordless phone and an audible beep is heard. The actual button on the phone is never pressed to cause the beep or start the call.