Adjusting latch retraction in front door

[Jeppe]

I've got a front door where I'd like the latch to retract a bit more when the door handle is pushed down or the key is turned. This is how much it protrudes when the door handle is fully depressed:

It hardly clears the backing plate when opening the door:

Is this something that can be adjusted? We had a day where the door was difficult to open due to this, to the point where I at one point couldn't open the door with the key from the outside!

This is what it looks like when looking at the edge of the door:

 

[crank39]

The main gearbox is worn inside, there is no adjustment, it requires a replacement gearbox

 

[Jeppe]

How difficult is it to replace the gearbox? Is it something I possibly can do myself or would it require a locksmith?

I can see replacement gearboxes seem to come in at around £30, but I'd like to also not be left with a front door I can't shut in case I do something wrong while trying to replace it.

 

[crank39]

First you need to identify the make of lock as there are numerous manufacturers, hopefully somewhere up and down the lock strip there will be a makers name, that's your starting point, you may need to remove the complete mechanism to view the gearbox if the manufacturer has different styles which most do

Or you could employ a service engineer like me to do it and replace the gearbox, some gearboxes are £30 like you say but some can be £100, some gearboxes can not be split from the main mechanism so a complete replacement is required

Where are you based..... county only not a full address, most places have a window/doctor doctor that specialise in repairs

 

[Jeppe]

I found a couple of videos of people doing similar work to doors and had a go at opening up the mechanism myself. I found a new replacement gearbox that looks exactly identical to the one we have, which I have ordered. It shouldn't be too difficult to replace when it arrives.