Certain textures won't load sometimes
This is exactly my issue as well, it’s noticable in Windowed Fullscreen mode and only happens on the first load of the game after a boot.
I don’t think it has anything to do with alt-tabbing, or Windowed Mode, or anything else. This ‘bug’ showed up after a recent release, and is affecting many, many users. I do none of the things listed, and have the same issue. There are several threads about this.