Sometimes I enter the Pandoran's turn


Sometimes after I finish my turn, I get into the Pandoran’s turn, where I get to make a single move. I see this from the fact that on the bottom left I see the Pandoran characters listed, and I can cycle through them with TAB. After I make a single move, the game get’s stuck and won’t move forward. The ‘END TURN’ button is visible on the top of the screen but doesn’t do anything.

If I reload the save prior to ending my turn, I get the same behaviour.