Door latch not retracting fully

[RrogerD]

UPVC front door. When I press the lever handle the latch does not retract fully. It remains protruding by about 5mm. Is this normal and the fault lies elsewhere?

If this is the issue then do you know if it possible to just replace the latch operating mechanism (presumably this sits inside and behind the main linear plate of the door edge) or, will I have to replace the whole mechanism down the full length of the door, to include the upper and lower roller 'bolts' and hooks?

 

[crank39]

It's a common wear indicator, if the centre gearbox can be split from the main mechanism then its pretty straightforward, if there are 2 or 3 little torx headed screws around the area of the gearbox roughly no higher or lower than the handle backplate then it's removable however some gearboxes are riveted or peened on

 

[RrogerD]

It's a common wear indicator, if the centre gearbox can be split from the main mechanism then its pretty straightforward, if there are 2 or 3 little torx headed screws around the area of the gearbox roughly no higher or lower than the handle backplate then it's removable however some gearboxes are riveted or peened on

Thanks for the useful advice.
It would appear that there are the small torx screws present as you mention so fingers crossed....
The next difficulty is in finding one to suit. It is a 28mm backset, which I think is fairly old if not obsolete.

Presumably I have to remove the full strip from down the full length of the door and then extract the mechanism from this?