The motor whirs, strains, and gives up. Or the app says locked and the door pushes open. A smart lock that will not lock reliably is a security problem rather than an inconvenience, and it is worth fixing properly rather than working around.
The short answer
Test the deadbolt by hand with the door open and again with it closed. If it is noticeably stiffer with the door closed, the strike plate is misaligned and the motor is fighting the frame. Adjusting the strike plate is a twenty minute job and it fixes the large majority of these, along with the battery drain that usually accompanies it.
The alignment test
Do this before anything else, because it takes two minutes and it identifies the cause most of the time.
- Open the door. Turn the deadbolt by hand or with the key. Note how it feels: it should move freely with almost no resistance.
- Close the door. Do the same. If it now requires noticeable force, the bolt is catching on the strike plate or the frame.
A human barely registers that extra resistance. A small motor running on AA batteries registers it enormously, and the result is a lock that strains, retries, gives up, or reports success without having fully thrown the bolt.
Mark where the bolt is hitting
Rub pencil lead on the end of the bolt, close the door, and throw the bolt until it stops. Open the door and look at the strike plate: the graphite mark shows exactly where it is catching.
Adjust the strike plate
Unscrew it, and either reposition it a few millimetres or enlarge the hole with a file so the bolt passes freely. Refit and test by hand with the door closed. It should now feel the same as it does with the door open.
Tighten the hinge screws
Doors sag over years as hinge screws loosen, which drops the bolt below the strike plate. Tightening them, or replacing the top hinge screws with longer ones that reach the frame studs, often lifts the door back into alignment.
Check for a swollen frame
Timber frames swell in damp weather and shrink in dry. If the problem is seasonal, that is why. Easing the strike plate slightly wider gives you tolerance in both conditions.
Lubricate the bolt and cylinder
Use a dry graphite or PTFE lubricant. Avoid oil-based sprays in a lock cylinder, which attract dust and gum up over time.
Fit fresh lithium batteries
Low batteries mean less torque, and less torque means a lock that cannot overcome even slight resistance. Lithium cells hold voltage better under the brief high-current pulses a lock motor draws, especially in cold weather.
Recalibrate the lock
Most smart locks have a calibration routine that teaches them the locked and unlocked positions. Run it after any mechanical adjustment, or the lock will keep using the old positions.
Check the mounting is tight
The lock body and the thumb turn adaptor must be firmly mounted. Any play there means the motor turns and the bolt does not follow properly. Check every screw on the interior assembly.
If the app reports locked but the door opens, stop using the lock’s reported status as security until it is fixed. A lock that thinks it has thrown the bolt when it has not is worse than no smart lock, because it gives you false confidence.
Auto-lock making it worse
Auto-lock is where misalignment shows up most, because the lock fires with the door possibly not fully closed. If auto-lock is triggering while the door is resting against the latch rather than fully shut, the bolt has nowhere to go.
Two fixes: increase the auto-lock delay so there is time for the door to be pushed fully closed, and if your lock supports a door sensor, fit it so the lock only fires when the door is genuinely shut. That sensor is the difference between auto-lock being reliable and being a recurring problem.
When it is the lock rather than the door
- The motor sounds different from when it was new, higher pitched or laboured, with no change in the door.
- It fails the same way in both directions even with the door wide open.
- The thumb turn spins without moving the bolt, which means a stripped gear or adaptor.
- It works only immediately after fresh batteries and degrades within days despite good alignment.
Most smart locks carry a multi-year warranty, and a fault documented with dates and battery brands is a reasonable claim.
Why does my smart lock jam?
Almost always the bolt catching on the strike plate because the door has dropped or the frame has moved. Test by hand with the door open and closed to confirm.
Why does the app say locked when it is not?
The lock reports based on how far the motor turned, not on whether the bolt actually engaged. If it stalled partway it may still report success. That is why fixing alignment matters rather than tolerating it.
Does a misaligned door drain the battery?
Substantially. The motor draws many times more current forcing the bolt than moving it freely, and it is the most common reason a lock eats batteries.
Should I use auto-lock?
It is convenient, and it exposes alignment problems because it fires whether or not the door is fully closed. Increase the delay, and fit a door sensor if your lock supports one.
What if the batteries die while I am out?
Most locks have a physical key override, and many have external contacts where you can hold a battery for emergency power. Find out which yours has before you need it, and keep a key accessible.
The bottom line
Test the bolt by hand with the door open and closed, because that identifies misalignment in two minutes and misalignment is the cause most of the time. Adjust the strike plate, tighten the hinges, fit lithium batteries and recalibrate. If the app reports locked while the door opens, treat that as urgent rather than annoying.
