So, I was facing off against an enemy with a merc in my fleet and he had one ship and a merc. My ships made short work of his ship and then it came to merc vs merc with mine as support. The moment my merc fired at his, the game crashed. No error message, no nothing. Just quit the game to desktop.
I had The Path of Rhuin and he had The Bitte.
I had no crash when using quick battle, but this shouldn't be a necessity.