Lighting Issues

So I'm having a couple of issues I've never experienced while playing before...

- Anywhere that natural light hits on decks, the light flickers. This doesn't happen on terrain only decks and it happens at either day or night time in any mode 

-There is an artifact of sorts right in front of the railing on my porch. It is a flat white plane and is only visible when looking at it from the front of the lot

-My game has been crashing randomly while in Build/Buy mode. It's only happened twice but it's never crashed on me before. 

My graphics options are all set to medium even though my computer has no problems running HD videos and other games at 200 fps. This started after my recently downloaded of some more custom content but I had cc installed prior to this happening and all of those files are from trusted sources I've downloaded from before. Any ideas what's causing these issues and how to fix them? Thanks!