In article ,
Chris J Dixon wrote:

http://i64.photobucket.com/albums/h1...ates/door3.jpg

Have you tried tightening all the screws holding the frame to the
surrounding brickwork. If it has worked a little loose

Or indeed, taking off the lock plate, cleaning surfaces up, and then
reinstalling it nice and tight: that pic looks as though it's only the
lock plate which is catching.

J