To prevent this, always push hard on the door, squeeze the handle and then pull.
If it sticks, shake the door in/out to free it up.
Or push on the door while rolling the handle with your thumbs back into the unsqueezed position.
One of the problems is the door sticking shut, the other is the handle sticking in the squeezed position preventing you from trying to open the door again or keeping the door open.
This fix pictured below is the addition of a spring (I just used some old spring off a series LandRover) which forces the lock handle to return to the unsqueezed position. The prevents the need to roll the squeeze handle back to the unsqueezed position so you can try to open the door again (after a push on the door).
Unsqueezed position below with spring in place
Squeezed position below with spring in place
