I agree that it seems to come up more often. AFAIK it means that the server that takes care of players between games has been switched to another instance. When the game ends, the old instance is no longer there, and it can't show the end-of-game screen.
It doesn't affect ratings, the result has been recorded and will be taken into account if the game was rated. If I'm interested in the details of the end-of-game screen (like who had more Curses or won a Village split), I copy the game number from the "fixed" screen, then relaod the page, which brings me to the login page. After login, I load the just finished game at the end, and the we (me and my opponent) can study the end-of-game screen.
