Sliding door not locking from outside

[Tomc1958]

Apologies if this is the wrong place to post this.  1983 T25 RHD sliding door lock won't lock by key from the outside and when I lock it on the inside I can still open it from outside.  I've taken out the entire mechanism, de-greased/cleaned it. greased it all back again.  All parts move smoothly as they should but once it's back on the van the problem persists.  I bought a complete replacement locking mechanism, door catch, connecting rod/wire and rear catch.  All worked smoothly on the bench but when in the door I can still open the door from the outside when it should be locked.  Anyone know what's going on?  I've adjusted the tension on the connecting wire between the two parts of the mechanism...rear edge of the door and front edge but still no joy.  The only upside is I now have two fully functioning door locking mechanisms but I can't get either to work properly once in situ.  I'm stumped.  I've also tried two new door handles (with door grommet" and the inner "bolt" slides in both directions without problem and locks the mechanism when on the bench.  Basically, I can open the door from outside even when it's supposed to be locked.  Many thanks in advance

[davidoft1]

I probably have one , can take a look

[Tomc1958]

I probably have one , can take a look

Hi and thanks.  It's not a broken mechanism, I've tried two and two new handles.  It's got to be something about how I've got it adjusted but I can't work out what.  Thanks anyway
 

[slowcoach]

With the outside door handle removed, can you lock and unlock the door with your finger, by pushing the lock ring left and right?

Sent from my Pixel 4 using Tapatalk

[Tomc1958]

With the outside door handle removed, can you lock and unlock the door with your finger, by pushing the lock ring left and right?

Sent from my Pixel 4 using Tapatalk

Hi, yes, just been out trying again.  I think it's possibly a combination of worn rear catch and not quite the right adjustment on the tensioner between rear catch and handle mechanism.  Seems it needs to be quite precise.  I'm going to have another go with the replacement I bought when it's a bit warmer.  From looking at breakdown illustrations of the mechanism online I'm missing a small shim/washer with a square hole in it which slides over the square handle spindle.  Even without that though the bolts through the handle still push the insides of the internal lock ring