Cant Remove Key After Locking UPVC Door?

Hi there,

Im at wits end I have a problem with my upvc door in that upon locking the door the key does not go around far enough for removal, meaning that when leaving the house if I want to lock the door I have to leave the key in the lock.

I have replaced the lock itself along with the barrel neither of these replacements have solved the problem, I have also tested the lock outside of the door environment and the same problem exists. any ideas?