Continuity mistake: When John Strode goes downstairs, his hair goes from dry, to moist/wet looking and hanging down.
Plot hole: Jamie takes off running with her baby. 33 seconds later, Michael kills the nurse. 30 seconds have passed since killing the nurse and Michael is right behind Jamie and somehow manages to find a knife along the way. All in a one minute 5 second time frame. (00:04:50 - 00:05:55)
Continuity mistake: As the film progresses towards the third and final act, Michael's body goes from large and muscular to lean and thinner. No attempt is made to hide this. The reason is because the director decided to change the ending but didn't bring in the original actor, instead choosing a second one whose body doesn't match.