Test it with a spare key and make sure that.
Front door not locking from inside.
If a strike plate is recessed as often happens when the doorway is painted several times remove the screws pull it out and make cardboard shims to fit in the mortise.
There are three main reasons your door is rattling.
When the door is shut the striker.
To resolve the issue of not being open from the inside check for issues in the power locking system.
Have you had a new cylinder fitted.
Privacy door knobs are locks for the doors in your home.
These are relatively cheap to replace although i would recommend ensuring it has at least a 1 star rating and best of all a 3 star rating.
Key will not work if you ve had a new spare key cut recently it could be a poorly cut key causing the problem.
Sticking door locks can be attributed to everything from slight settling of the house to a buildup of dust and dirt within the locking mechanism.
Not for high level of security needed for exterior doors.
Privacy door knobs have a push lock or twist lock on the inside of the room.
And finally check the lock assembly for broken parts and double check the door lock motor.
If you re referring to a upvc door then the chances are that the internal half of the euro cylinder has something faulty with it.
The strike plate is recessesd the latch bolt does not align or the strike plate needs to be reset.
This entire process is easily done with the door panel removed.
Here are the basic steps on how to fix this problem.
First you will need to work on removing the broken key pieces from within the keyway of your door lock.
A rim automatic deadlatch nightlatch is fitted on the inside of your door with the key locking cylinder to insert your key to open the door located on the outside of the door.
It may require repair or replacement.
Locked and unlocked from both sides with a key inserted in a rim cylinder.
Fortunately most front door lock problems can be.
Once the key pieces have been extracted the door lock should be examined.
Quite easy to replace but if in any doubt call a locksmith.
You will find deadlatches commonly referred to as nightlatches and yale locks as well.