Factual error: In the very first shot of the movie, a clock is shown ticking. The time on the clock reads 05:59:56. It is obviously AM because a few seconds later at 06:00:00, Frank wakes up as if it was morning. As Frank sits up, clear daylight is visible outside of the window. This scene is supposed to be set during winter. We know this because there are many Christmas decorations. Since this is meant to be winter, it should still be dark at that time of day.
Continuity mistake: After killing all of the assassins, Frank places bullets in a frying pan and turns the stove on. When the bullets go off, the rest of the assassins start shooting at the house, destroying a snowman on Frank's porch. In all future shots of the porch afterwards, not only has the snowman disappeared, but there's also no sign of the snowman's remains either.