Retreating and dying. Is this a bug or my ignorance ?

[Man with No Name]

Once a unit successfully retreats from the battle they are dealt with the same. It makes no difference if they fled or were ordered to retreat. And you can only retreat to friendly provinces. I do not know why Gandalf Parker remembers otherwise, but it is a mistaken memory.

A video of the battle is not going to be enough to provide you with an answer I'm afraid. That is like asking a mechanic to tell you what is wrong with your car by taking a photo of it. The mechanic has to see the car, and we will need to see the turn file. So unless you can post the turn file, I do not see how anyone can offer you an explanation as to what happened, or confirm whether there is indeed a bug involved.