I had this issue all day but found a solution and now I load in to all fights (fingers crossed); figured it may help some others. Essentially, all you have to do is allow more power to your GPU, method may change based on make/model, so I suggest just googling "how to change power settings with (insert Make/Model)". I wouldn't recommend to change it in general settings, but you can specify it to apply maximum performance (or maximum power limit, depending on terminology) for just Bannerlord.
Hope this helps!
Hope this helps!