It’s not a ghost that keeps opening that door by itself. It could be something even scarier, such as significant structural movement. Now that can be scary!
Doors that open (or close) all by themselves can be a red flag and may mean significant foundation settlement or even foundation damage. I ran into this just a couple of months ago on a home inspection in Redwood Shores. All of the doors on the left side of the home would swing open or shut by themselves. The second floor was more pronounce than the first. This is not just an issue with Redwood Shores, and this kind of scenario can be found in virtually every Bay Area city.
Generally speaking, the newer the home, the more this may potentially develop into a real problem. Most homes tend to do most of their settling during the first 5 years of original construction. A newly built home that is already showing significant structural movement in the first year may be in for a future of trouble.
Certainly, a little leeway needs to be provided for common house settlement and lumber drying (doors and door trim are installed dry but the surrounding door framing may have been installed wet). Three days ago I inspected a big home in the Los Gatos mountains that had huge doors with undersized hinge screws. The screws at the top hinges were pulling out of the door, and the result was badly binding doors. This is not an indication of structural movement, but of undersized fasteners.
Installers who hang doors will (HOPEFULLY) make sure the door operates properly prior to finishing the job. Any door that binds after the installation indicates the structure has moved to some degree. This is more related to interior doors. Exterior doors a more prone to swings temperature and humidity which can swell and contract wood cyclically. Doors that operated fine in the summer swell when the rains come and can bind in the winter. This can actually happen on interior doors as well, but to a lessor degree since the home is generally climate controlled. Cabins in Tahoe that are unoccupied for extended periods can experience more door issues than we have in the Bay Area.
Another clue to look for are doors that scrape the floor, or are shaved at the top edge (usually at the corner). Try running your hand along the upper edge of the door and feel if it has been shaved. If many of the doors are shaved then that is a big red flag. Look how the door sits in the frame. Are the gaps more or less uniform or is one corner gap much bigger than the others?
If you come across a home with binding doors, make sure you hire a qualified home inspector for further review. He or she in turn may recommend that a structural specialist be called in.