Cannot Lock uPVC Patio Doors from Inside

[Hank80]

Hi,

This started a few days ago. We can lock the doors from
outside the house but not from the inside, the key is not
turning round in the lock as it usually does.

Any idea what may have caused this? and can we
fix it ourselves?

Many thanks for any help!

 

[Gazman16]

Most likely the barrel "Euro cylinder" is on its way out (assuming thats what you have).

Post a pic to confirm.