You have been lifting the door slightly for years without noticing. The motor cannot do that.

Test the old deadbolt honestly before you buy anything

Close the door properly and throw the existing deadbolt with one finger, slowly, without touching the door with your other hand. It should travel the whole way with no resistance and no help. If you find yourself pulling the door toward you, lifting the handle, or pushing a shoulder into it, the door is out of alignment and a motor will not be able to do what you just did. This takes ten seconds and it is the single most useful thing on this page, because it tells you whether you are buying a lock or booking a morning of door work.

The lipstick test tells you exactly what is wrong

Put lipstick, chalk or a grease pencil on the end of the extended bolt, wipe the strike clean, close the door and throw the bolt so it marks whatever it hits. Open the door and read the mark. A mark below the strike opening means the door has sagged on its hinges. A mark to one side means it is hitting the inside or outside edge, so the door is sitting too far in or out. It converts a vague complaint about a sticky lock into a specific measurement in half a minute, and it works just as well on a latch as on a deadbolt.

Move the door before you move the strike

The instinct on finding a misaligned bolt is to unscrew the strike plate and move it to wherever the bolt now lands. That chases the symptom, leaves the door still hanging wrong, and often makes the latch above it worse. Work in this order instead. First, if the door has sagged, shim behind the bottom hinge or replace the hinge screws with long ones that reach through the jamb into the framing, which pulls the whole door back up. Second, many strike plates have a small adjustable tab on the inner edge that a screwdriver will bend, which shifts where the closed door sits by a small amount. Only after those should you reposition the plate itself.

Plug the old screw holes or the strike plate walks back

This is the trap in relocating a strike, and it defeats people who did everything else right. If the new screw position is close to the old hole, the screw finds the path of least resistance, wanders into the old hole, and drags the plate back to precisely the position you were trying to leave. The fix is old and reliable: glue a wooden dowel or a golf tee into the old hole, snap it off flush, let it set, and then drill fresh. Ten minutes of waiting saves an afternoon of wondering why the plate will not stay where you put it.

Measure the backset, because the bolt is adjustable and the setting is wrong by default for half of doors

Backset is the distance from the edge of the door to the center of the bore hole, and in American doors it is one of two numbers: 2 3/8 in or 2 3/4 in. Schlage’s instructions say to measure it, and that at 2 3/4 in (70 mm) you extend the bolt. Getting this wrong is one of the most common reasons a new lock will not seat correctly, and it is easy to miss because both settings let the parts go together. Measure rather than assume, use the bolt supplied with the lock as Schlage specifies, and note the faceplate twists between round-corner and square-corner so it matches the mortise already cut in your door edge.

Door open, hand tools, and drill the strike pilot holes deep

Schlage puts two warnings up front and both are worth respecting. Install with the door open, so that a partially assembled lock cannot leave you shut out of your own house. And do not use a power drill for the installation, because these assemblies are held by machine screws into soft castings and a drill strips or overtightens them faster than you can react. The one place drilling belongs is the strike: 1/8 in pilot holes, 3 in deep, two of them. That depth is deliberate, because a 3 in screw passes through the jamb and bites the framing behind it, which is what makes a strike resist force rather than tearing out with the trim.

Retrofit or replacement is a decision to make before you order

A retrofit lock replaces only the interior thumbturn and leaves the exterior cylinder and your existing keys alone, which is the right answer for a rental, a door with hardware you like, or a household that wants to keep using keys. It only works with single-cylinder deadbolts, the ones with a thumbturn inside, and the adapter has to suit the brand of the existing lock, with the tailpiece rotating freely in it rather than binding. A replacement lock changes the entire assembly and usually brings a keypad. Both still depend completely on the door being aligned. Separately, check whether the model you want has Wi-Fi built in or needs a separate bridge plugged in near the door, because that is a purchase decision people discover afterward.

Ten cycles, both sides, every method

Testing a smart lock once from the inside with the door open proves almost nothing. Close the door and run at least ten full lock and unlock cycles, from both sides, using every method the lock supports: the app, a keypad code, the physical key, and the thumbturn. What you are looking for is any cycle where the motor sounds like it is working harder, any hesitation, and any time the bolt does not travel fully. One sticky cycle in ten is not a fluke, it is the alignment problem showing itself, and it will become ten in ten in the first cold snap. Set auto-lock only after the mechanical side is clean.