With the door open try to lift the rear of the door while watching the middle sliding hinge, see if there is much play in the brass bushes, it looks to have dropped at the rear ?
Come to techenders! @davidoft is our official sliding door and sunroof king. Liking the awning rail just under the canvas line
Lifting the rear door I cannot detect much if any bush wear but can lift the roller mechanism about 1-2 mm off the rail. I cannot see how this is adjusted or would the roller itself be worn?
Where the hinge slots into the door it's held by 4 small bolts. 10mm spanner. Get someone to help. Slacken the 4 bolts and lift the door. Keep the door held and tighten the bolts. That might take up some of it.
Thanks - did this. Perhaps made a very slight difference, maximising the adjustment in the right direction. Might have to live with it for the season... Cheers
All sorted and thanks to @zedders for additional info on adjusting the strike plate on the door pillar up a bit which did the trick. When door is closed it’s position relies on this strike plate not the position of the roller.