The WD40 was sprayed into the physical door jamb latch side. My thought was that maybe the tight new cable forced the mechanism into a spot that it hadn't seen in a while and wasn't releasing when the door handle was being pulled.

Both inside and outside door handles were rendered completely useless. I reached up in the door and manually pulled the levers for both inside and outside handles. I could hear the door latch unlatch when pushing the lever, but the door remained stuck.

I snapped the ball on with pliers and it appears fully seated. It has full range of motion wiggling side to side to all extremities you'd expect from a half cup on a ball socket.

I just spent 15 minutes opening and closing the door in every combination I can think of to cause a problem... Hold inner door handle cable tight while closing the door and trying to open it. Various combinations of lock and unlock patterns. Prevent the outside handle lever from going fully into the relaxed position when latching and locking the door. Pull the slack out of the door handle cable while going through the entire close door, lock, unlock, open procedure.

I cannot replicate the problem of the door getting stuck closed.

The closest reference to the symptom I found is a thread somebody posted elsewhere that went unanswered, and a thread somewhere about the door lock freezing in ice climate and bring resolved with soaking the door latch exterior area with hot water and subsequently lubricating it to prevent future freezing.

The fact that neither inside nor outside release mechanisms would release the door, even though I could physically feel and hear the mechanism doing its job, is what leads me to believe the latch that holds the pin got stuck.

But I'm no locksmith and haven't had time to re-read your above referenced threads with fresh eyes yet. Maybe it's not possible for that part of the mechanism to get stuck?