Common reasons doors stop locking properly

Weather, age, hinges, and building movement can shift the door enough that the latch or bolt no longer meets the strike plate cleanly. The lock may feel stiff even though the internal mechanism is still sound.

If the key needs jiggling, works only at a certain angle, or feels rough in the cylinder, wear may be building up. Early repair can prevent the key from snapping or the lock from jamming.

Loose screws, handles, escutcheons, or cylinders can place strain on the lock. Tightening and adjustment may solve it, but damaged parts should be replaced.