I have submitted a ticket on this.

Around turn 250 (immense game with a number of opponents, a couple custom races and minors)  I have started increasingly to have apparently random problems with the battle viewer presentation.  It happens only once in a while, and I can reload the game without any other changes, do the same attack, and it may work!    When it doesn't I get a black screen.   I hear the battle sounds.   When they finish I have tried to exit the screen in two ways: first by remember the location of the "done" button (this doesn't work) or by ESC, which sometimes does nothing and sometimes gives an error message.

Curious if anyone else is seeing this --- I think I have seen related posts but I haven't been able to find them.   Maybe I need a lesson in "search", lol.