weird fog of war bug, lag, and graphical bug

[ch1046 1]

i have fog of war off and my game was fairly normal untill i hit the 240 turn mark then all of a sudden i can still see nations from far distances but i can view their diplomacy with other nations nor can i see the political stability so i can see anything other than nations borders if they are far away. also for some reason after running some games for only a few hindered turns everything starts to lag badly. This has only every happend when i hit the 800-1000 turn range it only started after a update either a few weeks or 2-4 months ago. (i dont remember when that update happend). and when i was checking to see what i could and couldn't see for the bug i mention previously here it lagged then screen went white with the crash text displayed then the who screen blurred (like the text got blurry and looked pixalated). Anther bug i have seen is when the whole screen freezes execpt for the top or bottom part the game is still running and working is just that most of the screen is still and not moving i usally fixed this with me moving my mouse to the bottom of the screen and pull up the taskbar and everything goes back to normal. What is going on these glitches are happeing ever since a update recently.