I think action have problems with AMD drivers or something because also Mount and Blades: Warband(dx11) crashes when recording. Whole computer have to boot from power button. 2 times I have been able partially restore computer from crash so I saw error raport. It was something about "THREAD_STUCK_IN...
Action does not to seem support gaming record mode on TW:Warhammer. Can record if run game on window and use desktop record mode. Then Cursor does not show up and one cannot see record HUD.