I have just fixed mine.
I was hoping to do a guide for this last week....no time.
I had the door card off for another job (check strap), both front door handles were sticking up.
I took the handle off. I could then easily see that it is sticking on the handle itself, and not the door lock mechanism, that causes the problem.
The handle part is connected to the backing plate by two splined pins. The splined parts are in the handle part. The round parts rotate in the backing plate. Corrosion on those pins creates extra friction, this prevents the return spring from returning (closing) the handle.
I soaked mine in oil for a few hours, this helped loosen the corrosion. But the handle was still sticking.
I then drilled two small (2-3mm holes) in the pin housing on either side. This allowed:
1. Oil to penetrate to where it's really needed.
2. Me to lubricate the handle properly when reattached to the car
The second point is very important. It is almost impossible to lubricate the joint properly when the handle is attached to the car, lubricant does not really get to where it is needed.
That's why many people struggle in freeing the handle properly when spraying with WD40, etc.
Now the handle works properly, I can lubricate it properly when needed, and I didn't have to buy a new handle.
Nice....