That having been said, I remember that the doors of footlockers will open around a random vector in the xy plane. Most of us orient footlockers along the x or y planes, but there was one in Outpost that was not set up that way, and it works fine. I think the math uses the local axes orientation of the door rather than the world axes when opening.
Maybe there's hope in grabbing a footlocker prefab, rotating it so the door angle matches the cellar door angle, and see what happens when you open it. If that works, perhaps the attributes of the footlocker door can be transferred to the cellar door. Dunno, but it's worth a try before hiring a scripter.