Does the Door Lock with the Door Open?

This is one of the most common faults on both uPVC and composite doors. If your door locks with the door open but not when it's closed, it's usually a strong indication that alignment rather than the lock is at fault. This is explained in more detail in Door Works Open but Not Closed.

Has the Door Dropped?

Instead of locking smoothly, the mechanism begins to bind. Even a few millimetres of movement can place constant strain on the locking mechanism, which is why Why Door Alignment Matters explains why alignment should always be checked before replacing parts.

Has the Gearbox Failed?

Many gearboxes can be replaced without changing the complete multipoint mechanism. However, it's important to diagnose the fault first, as not every locking problem is caused by the gearbox. Every Door Problem Isn't a Lock Problem explains why.

Is the Euro Cylinder Faulty?

If the problem occurs whether the door is open or closed, the cylinder may require replacement. If the key is also difficult to remove or only turns part of the way, those symptoms can help narrow down the cause. See Why Is My Key Difficult to Remove? and Why Does My Key Only Turn Half Way?

Could the Handles Be Causing the Problem?

Replacing the handles may restore normal operation if the gearbox is still functioning correctly. A stiff handle shouldn't be ignored, as it often puts extra strain on the internal mechanism. How a Stiff Handle Can Lead to Lock Failure explains why.

How a Locksmith Diagnoses the Problem

This systematic approach helps identify the true cause of the fault. Professional diagnosis follows a logical process rather than replacing parts by guesswork. If you'd like to understand that process, see Door Lock Troubleshooting Guide.

Most Door Lock Problems Can Be Repaired

Many homeowners assume that a door which won't lock needs a completely new door. In reality, most faults are caused by alignment issues, worn gearboxes, damaged handles or failed cylinders rather than the door itself. These components can often be repaired or replaced individually, restoring smooth operation and security without the cost of fitting a new door.

If your lock feels stiff before it fails completely, Why Is My Door Lock Stiff? explains the common causes. If the door only locks when you lift the handle, Why Won't My Door Lock Unless I Lift the Handle? covers that fault in detail. For a broader overview of the symptoms you might encounter, Guide to Door Problems, Common Door Lock Problems, and Common Lock Faults Explained provide further guidance.