I died couple of times trying complete this mission, not sure if it has anything to do with it, but it does mean that my last attempt to complete the mission was after the game loaded from the Hanged Man's Tree (where you and Roche rush to save Ves). Also it took the cutscene a bit longer than I think it would normally take to trigger. If somebody from the development ever gonna read this, I've noticed something weird that might be the cause of it: The last opponent I killed (or Ves killed or whatever), a heavy armored Nilfgaardian soldier, had a red text over his body as if he was alive and in combat with me. Got the same problem, after the same mission, though I played on version 1.06 (it didn't happen on my first playthrough of the game in that mission, which was a different version though I don't know which).
Shame there is no answer from the game developers.