In the news articles about the Howe murders, the father is named Robert Howe. When Hannah is reading David's medical records, the father's name is Michael Howe.
After Hannah has fallen asleep and the bed covers are pulled down, her hands move places with different camera angles; sometimes on her hips, other times high and low on her abdomen.
When Hannah discovers the hospital files for the mysterious psych patient, the prop form used has a prominent misspelling on the header, reading "PYSCHIATRIC REPORT"
One major flaw (among many) of this movie was the existence of wide spaces between the walls and floors that allowed our mystery villain to be able to move silently and easily between the attic and the other floors. Construction of homes in the last 50 years does away with these spaces, reserved for pipe chases and duct work.