During my playthrough of the prologue the game crashed to Desktop twice immediatly I think somehow related to the Alt+Tab issue or similar (using Steam or Game DVR overlays) and once the tutorial displayed an overlay darkening the screen and an arrow pointing to the garrison icon or where it should be, because the settlement HUD wasn't there but it was a required step for the tutorial to click the button else the tutorial would not move on and the overlay would not disappear. The overlay disabled all other UI and keyboard inputs, Esc didnt work, I was forced to exit the game from outside.
See screenshot

Then I've had the Alt+Tab issue with the game freezing, I waited patiently but it doesn't recover and cannot be stopped by Alt+F4, the game window is always being forced on top, I can't use Task Manager to end the process and have to restart Windows.
I think it was then when I had received the mission to use the ice maidens campaign ability on either an enemy army, agent or settlement. After the crash when I reloaded the save next turn the message appeared the mission was aborted and I immediatly received the same mission again. I was never able to complete the mission thereafter albeit having tried and used it on enemy armies, agents and settlements alike. (Perhaps the German translation is wrong or unclear, it says 'target an enemy army, agent or settlement with the Ice Maidens ability' in other instances a similar mission reads 'Successfully assassinate/wound/etc target agent')
I configured F7/F8 for decrease/increase speed in battle but it doesn't actually work, K for hiding UI has also stopped working once until I restarted the game.
After replacing a lord ice witch with another lord she was displayed bugged in the list of recruitable lords:

Some 20 turns later or so this was still the case when I recruited her again.