Blackscreen/crash on ambush battles

So far I've had crashes which only seem to occur during ambush manual battles. One is during the Skaven new DLC campaign the shadow and the blade. I try attacking with Skaven army which prompts him to ambush the enemy and when selecting manual battle after loading, the screen just goes black then glitchy, then black and there is still background music playing. I also get this crash when I play as the wood elves and my army ambushed a beast men army using the beast paths, except this time the battle loads and can partially play the battle, but occasionally it will black screen and go back to the battle, then all of a sudden black screen again permanently forcing me to exit the programme. Every other battle that I've had so far that isn't an ambush battle all work fine.

Build number is v 1.8.1
13089.1833768

Have attached dxdiag, preferences and log.