One side of our double fronted (double glazed last year) door is
unable to open as one of the latch that holds the door to frame is not
releasing properly.

We had this problem few times now and the double glaze engineer had to
come and fix it for us - The fix seems (?) to have been carried out by
adjusting the hinges...

1. Where can I buy the tools somewhere to adjust the hinges to fix the
problem...?

2. What normally cause this problem...? As its the third time, should
double company looking into fixing the underlying problem...? e.g.
replace doors ??!

Thanks,
Sandiyan.