Andrew Gabriel wrote:

In article ,
Mrs Bonk writes:
I have French doors and get the same. I work afternoons and dare
not open the doors in the morning as the sun hits them then I can't
lock the door to go to work.
On mine it is the bolt on the one door hitting the lock hole in the
central bit. I removed the offending brass section housing the
"hole" I still have two working bolts ( this probably voids my
insurance) I have the same on the back door this time I had to
remove two brass housing strips ( dunno the correct name) I fitted
two other security bolts instead. I did intend to replace
everything but moving it about eighth of an inch however, did one
which worked, then when the door cools- it doesn't bolt lol. I did
file one down and that worked but couldn't file enough of the other
one.

Check to see if the door has dropped by measuring the two diagonals
top to bottom corners. They should measure the same, and if they
don't, the door has dropped due to incorrectly fitting the glass
and/or panels in it, without healing/toeing them. Very common,
because the fitters often don't understand the process, and it takes
a while to fail after they've gone.
(Can also do the same check on the frame opening to make sure it's
square too.)

Thanks Andrew. I will carry out those checks. In answer to your
earlier question the locking mechanism works fine when the door is open
so I take it that it is either fouling at one of the points where it
latches into the "fixed" door or where it bolts into the top or bottom
of the frame. It sounds as if I am not the only one to experience
this problem. Fortunately it is only the porch, there is still a
sturdy old fashioned wooden front door behind it.

--
Tinkerer