Hi!
While in fight, I have a strange and pretty annoying bug: the tiles my brothers can’t see, which should be fog of war, are replaced by a graphic bug. But an picture is always better than my shaky english so here it is!
This bug happened in several games at every fight, but the very first one (probably because the map is fully discovered on this one).
Your Intel HD Graphics 4000 doesn’t clear the screen correctly. According to your DxDiag.txt, your video drivers are from 2012, so I suggest you update them to the most recent version from here.