Hi, quick update I uninstalled the game and then reinstalled this appears to have resolved the issue I am now back to full screen if the problem presents itself again I will post with any further information.
I am also playing the game and up to a couple of days ago it was displaying a full screen now it's gone to the same scenario you are having, as far as I am aware my windows 10 settings have not changed and as far as I am concerned my PC is exactly as it was from day one so unfortunately I cannot offer any solution but…