Icons Moves Around After Using Fullscreen Apps - Not Lined Up

I generally like to have a clean desktop -- so I put my desktop icons in a familiar location. The trash can always goes in the bottom right, important computer shortcuts / folders in the top right, etc.. However, (I can't say how long its been happening) I use a lot of fullscreen applications (games, mostly), most of the time launched from Steam. When these games exit, my icons are randomly placed. I've noticed that they tend to be close to the top right of the screen extending to the middle of the top. They are not all lined up, there are often spaces in between them.