The presence of brittle (low-quality) armor on late-war German tanks.
I was playing a dynamic campaign, and my Tiger II (H) kept getting frontally penetrated. Meanwhile, in similar situations against the same enemies, my angled Tiger I could shrug off the hits. The enemy was using 17-pounders. I found an old article Developer Blog #47 - Armour 2.0 from 2016 mentioning this, but is this actually still a thing in the game?
>Armour Flaws
>As the war progressed, important materials for armour production were rationed which would affect armour quality and penetration resistance. Also unskilled labor and poor quality control contributed to armour quality in certain situations. An example would be, American quality control permitted flawed armor in many tanks prior to October 1943, including Sherman front plates. It is possible the British underwent major quality control improvements around the same time. Many German Panther and Tiger II tanks suffered from medium to large flaws in their armour (especially Panther Glacis) which contributed to lower than expected penetration resistance.
Again, testing still needs to be done to determine which or if any of the armor types and factors will be in the finished game.