door lock

having a bit of an issue with the passenger door lock it has been fine for years but the other day the mrs shut the door holding the handle in to lock it . Now for some reason it wont unlock on the key ? will lock with the key but not unlock , locks/unlocks fine from the inside .
I have lubed up every part i can get too and its still the same , as you turn the key its like theres something stopping it turning . with the door open if i push the catch on the door itself as if you had shut it , it will lock/unlock fine on the key just wont do it with the door shut ?

Any idea's i can look at before i have to start stripping it down ?

thanks

 

Then the say it wont lock - does it turn but not lock or not turn in the that direction at all.

 

Did the handle bit she held spring back out again, or get stuck.

 

thanks for the replies but think ive sussed it apparently theres a small spring inside the latch mechanism which is a common fault for stretching/snapping and it allows you to be able to lock the door with easy but without some serious jiggleing you wont be able to unlock the door ! so will get camperjam out the way and order said spring as there still available

And zed the lock works fine from inside and can lock it fine with the key , or by holding the handle in which dosnt pop back out , its just purely unlocking as you turn the key to unlock it meets some serious resistance and feel like your gonna bust the key which would not be good ! hopeing it is the spring that has snapped as it has been fine for years

 

The spring in question is a very different length depending on whether you have inner lock pull up by the window, or as part of inner latch handle.
If the actual outer cab handle lever doesn't spring back, I'd prise it out and try the key again. When the little pring breaks, generally the key moves, but doesn't lock OR unlock the door. Worth a try as it's much more simple to fix.