I have 8GB of RAM, Intel i5 8250U. I was just booming hard with the Seleucids and this happened. Before this I played with the AI for 2 rounds and this did not happen. The game was very stable even when I was testing dodgy mods. It could just be my rubbish computer hardware or greedy Win10, but I feel like I should report it.  I don't have any mods installed, just built from the source code on Git.