I have written this to help others who may have this apparently common problem.
I started by removing the door card, this is to allow access to the connecting wire from the handle to the catch.
Then after opening the door I undid and removed the large philips head screws that hold the catch mechanism in place and removed the catch.
It was crudded up with 25 years of dirt so i cleaned all the cr*p out, then I noticed that the whole assembly was deformed....
you can see from the pic that it is no longer square, what must of happened is that either by time/wear and tear or more probable an incorrectly positioned striker bolt, it had become bent, not having a vice to hand I re shaped with a hammer.
The next thing I noticed was that the latch mechanism itself was bent....
again I reformed this with a pair of pipe grips
then I tapped this bit down ( on the tip of the screw driver ) this bit holds the latch and stops it moving from side to side. don't hit it too hard so that I doesn't move at all !
Finally I put it all back together, adjusted the striker bolt position and Voila the door shuts with a gentle push, perfect shut lines and NO popping open.
P.S I have read in other posts that It is necessary to remove the rear hinge to allow enough room for the catch to be removed, I didn't need to do this. Mine Is a later type door, if that makes a difference ?
