Following the respray the painters have refitted the sliding door which opens and closes great. I have a small issue though in that the top of the door is catching the top of the opening inside the aperture when fully closed, I have only just noticed this today. It would seem I need to drop the whole door probably a couple of mm to clear, is this possible?
Yes it probably is (depending on any repairs around the lower roller bracket). Line up the swage line and the rest should follow.
Before you undo any brackets or hinges, run a piece of masking tape along the sides and top and bottom of them so you can tell where they were in case you make things worse at least that way you can put it back to how it was. If you move the door down, the striker plate etc will probably have to follow it !!!